Company lists · Data refreshed September 2026
Top 25 Professional services outsourcing firms based in the United Kingdom
RevenueBase identified 517 professional services outsourcing firms headquartered in the United Kingdom as of September 2026 and tracks 5,840 professional contacts across them, including 1,808 with verified work emails. London is the largest hub.
This list covers professional services outsourcing firms headquartered in the United Kingdom, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Every row shows the company's own description, its RevenueBase Smart Search rating, and when it was last checked. Data refreshed September 29, 2026.
Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase Smart Search, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.
The 25 largest professional services outsourcing firms based in the United Kingdom
Ranked by team size| # | Company | Contacts | |||
|---|---|---|---|---|---|
| 1 | 870 contacts → | ||||
Partial evidence “At Oliver James, we deliver flexible hiring solutions tailored to your business needs across financial services, professional services, commerce & industry.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 2 | 477 contacts → | ||||
Partial evidence “Outbooks is a leading provider of outsourcing services to accounting and bookkeeping firms.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 3 | 333 contacts → | ||||
Partial evidence “Ubique Systems is a fast growing multifaceted organization which offers a comprehensive array of outsourcing and consulting services for its customers, including recruitment…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 4 | 322 contacts → | ||||
Indirect evidence “At SKS, we pride ourselves on being different.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 5 | 311 contacts → | ||||
Partial evidence “GI Outsourcing is a UK-based accountants outsourcing firm.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 6 | 146 contacts → | ||||
Indirect evidence “At The Dot HQ, we empower businesses with a full spectrum of offshore resource solutions, ensuring efficiency, compliance and growth.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 7 | 108 contacts → | ||||
Indirect evidence “As attention turns to the new fiscal year, accountants across the UK are finalising plans to boost growth and productivity and improve profitability.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 8 | 103 contacts → | ||||
Partial evidence “we redefine business process outsourcing, empowering companies to broaden their horizons.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 9 | 88 contacts → | ||||
Partial evidence “Founded in 2001 by lawyers, Global BPO provides bespoke legal and business services to law firms, professional service organisations and other businesses.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 10 | 70 contacts → | ||||
Partial evidence “We are a 400 member strong, specialist business process outsourcing (BPO) provider that caters to the diverse and complex information processing needs of todays corporation.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 11 | 64 contacts → | ||||
Indirect evidence “At MPA, we exist to help business owners navigate the complex journey of scaling and exiting their businesses.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 12 | 53 contacts → | ||||
Partial evidence “Passle powers growth at the world's leading professional services firms, including Ropes & Gray, Linklaters, Quinn Emanuel and many more.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 13 | 47 contacts → | ||||
Indirect evidence “Leading providers of specialist support services.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 14 | 42 contacts → | ||||
Indirect evidence “Diacron Group provides accounting, tax and corporate services.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 15 | 41 contacts → | ||||
Indirect evidence “Welcome to Factotum-your secret weapon for streamlined business success!” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 16 | 37 contacts → | ||||
Indirect evidence “Rödl & Partner – The agile caring partner for Mittelstand shaped world market leaders As attorneys, tax advisers, management and IT consultants and auditors, we are present with…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 17 | 37 contacts → | ||||
Indirect evidence “Charles Marcus is our multinational network of consultancy firms.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 18 | 32 contacts → | ||||
Partial evidence “Jayva Global provides a comprehensive range of consultancy and training services to law firms and professional service organisations throughout the UK, USA, Ireland, New Zealand…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 19 | 32 contacts → | ||||
Indirect evidence “Briars - Scale Locally, Expand Globally 30 Years in Business, 150+ Years of Combined Expertise Trusted by Clients Global Coverage across 100+ Countries At Briars, we are your…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 20 | 32 contacts → | ||||
Partial evidence “Almost every business can save time and money with smart outsourcing from Go-To - how much depends on you.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 21 | 31 contacts → | ||||
Partial evidence “Connect Systems are based in Chesham Bucks and were established in 1992 to provide professional IT services to the SMB market place.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 22 | 27 contacts → | ||||
Partial evidence “WTS Hansuke is a specialist professional services firm notable for its focus on excellent client service and agility.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 23 | 27 contacts → | ||||
Indirect evidence “Now part of the Lawyers on Demand offering within the broader Consilio family.” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 24 | 26 contacts → | ||||
Indirect evidence “KBM Group was founded as a Chartered Certified Accountancy firm, offering advisory and consulting services for business start-ups and organizations looking to strengthen their…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
| 25 | 24 contacts → | ||||
Indirect evidence “Oakford Advisors Ltd, a Centralis Group company, is an outsourced business services firm which specialises in providing back-office support to start-up or existing companies…” Source: RevenueBase Database · checked Sep 29, 2026Thanks. The Data Team will review it. | |||||
RevenueBase Smart Search
RevenueBase Smart Search assesses information from a company’s LinkedIn profile, information supplied directly by the company, its website, and other publicly available sources. It uses that information to rate how closely the company relates to this list’s category: professional services outsourcing firms. Every row carries its rating and the description the rating was read from, so each one can be checked rather than taken on trust.
- Strong evidence
- The company's own public description of its business names professional services outsourcing firms.
- Partial evidence
- Its own public description names part of professional services outsourcing firms, so it works in or next to the category without describing itself that way.
- Indirect evidence
- The description shown does not name professional services outsourcing firms. The match rests on the rest of the company's public profile rather than the one sentence quoted here, so this is the rating to check first.
RevenueBase Smart Search is how these lists are built: RevenueBase's data engine and AI assemble the companies that match a category defined in a user's own words, so a list can be about what companies actually do rather than about whichever industry code they were filed under.
Showing 25 of 517 professional services outsourcing firms based in the United Kingdom
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Professional services outsourcing firms based in the United Kingdom at a glance
As of Sep 29, 2026Companies by employee count
Email recency for this list is measured worldwide rather than for United Kingdom, so it is reported there. Company counts and contact totals on this page are exact for United Kingdom, over 517 companies.
How this list was built
Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among professional services outsourcing firms, so some rows will be adjacent to the category rather than pure plays. The description and RevenueBase Smart Search rating on every row are there so you can check each match yourself.
- Source
- The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase Smart Search, the natural-language company search available to every RevenueBase user.
- What qualifies
- Companies headquartered in the United Kingdom whose own description of what they do matches “professional services outsourcing firms”. Matching reads each company's description, not its industry code or its name.
- RevenueBase Smart Search
- RevenueBase Smart Search is how this list is assembled and how each row is rated. RevenueBase's data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to a category defined in a user's own words. Each row is rated strong evidence (its own description names professional services outsourcing firms), partial evidence (it names part of the category) or indirect evidence (the description shown names none of it and the match rests on the rest of the company's profile). The description supporting each rating is quoted on the row.
- What we exclude
- Companies whose own description does not clearly place them among professional services outsourcing firms, and records with no verified work email. Companies headquartered outside United Kingdom are excluded even when they keep an office there.
- Match quality
- In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and its RevenueBase Smart Search rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
- Ranking
- Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
- Verification
- Every listed company carries at least one verified work email, 1,808 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
- Refresh
- This page's figures were pulled from the company graph on September 29, 2026. Lists refresh periodically as the graph is re-checked.
- Corrections
- Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.
Professional services outsourcing firms by metro
Frequently asked
What is RevenueBase Smart Search?
RevenueBase Smart Search is how RevenueBase decides which companies belong on this list and how strongly each one fits. Its data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to the category the list is about. Each row is rated strong evidence when the company's own description names professional services outsourcing firms, partial evidence when it names part of the category, and indirect evidence when the description shown names none of it and the match rests on the rest of the company's profile.
How many professional services outsourcing firms are there based in the United Kingdom?
RevenueBase identified 517 professional services outsourcing firms headquartered in the United Kingdom as of September 2026, matched on each company's own description of what it does rather than its industry code.
What is the largest company on this list?
Oliver James, headquartered in Manchester, tops this list with the largest team on record.
Which city has the most professional services outsourcing firms?
London leads with 205 headquartered companies, followed by Manchester (17) and Birmingham (10).
How do I get contact information for these companies?
A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 1,808 verified decision-maker contacts tracked across these 517 companies.
How current is this list?
The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 29, 2026.
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About this data
RevenueBase is a B2B data infrastructure company. Its company graph covers 60 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph with RevenueBase Smart Search, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.
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