Company lists · Data refreshed September 2026

Top 25 Online advertising agencies based in the United Kingdom

Name: Online advertising agencies based in the United Kingdom
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Sep 5, 2026 7,756 companies tracked

RevenueBase identified 7,756 online advertising agencies headquartered in the United Kingdom as of September 2026 and tracks 45,951 professional contacts across them, including 10,114 with verified work emails and 2,736 with mobile numbers. London is the largest hub.

This list covers online advertising agencies 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, how directly it supports the match, and when it was last checked. Data refreshed September 5, 2026.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase SmartSearch, 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.

How to read this list HQ checked on every row Match evidence on every row Refreshed Sep 5, 2026 86% judged on-target in blind review

7,756Companies

45,951Contacts tracked

10,114Verified emails

2,736Mobile numbers

Unlock all 7,756 companies Free signup · no credit card · 500 free credits

The 25 largest online advertising agencies based in the United Kingdom

Ranked by team size

Top 25 of 7,756 online advertising agencies based in the United Kingdom, ranked by team size, largest first. Data refreshed Sep 5, 2026. Evidence rates how directly each company's own description names online advertising agencies: strong (names it), partial (names part of it), indirect (matched on its full profile rather than the summary shown). Click a count to unlock that company's people.
#	Company	Headquarters	Employees	Contacts
1	YELLIndirect evidence	Reading, United KingdomHQ checked Sep 5, 2026	501-1,000	1,284
	“Since 1966, we’ve been helping UK businesses grow – from printed ads in the Yellow Pages to powerful, AI-driven digital marketing that delivers real results.” Source: company website · checked Sep 5, 2026
2	M C Saatchi PerformanceIndirect evidence	London, United KingdomHQ checked Sep 5, 2026	201-500	457
	“We are a Global digital media agency specializing in taking a human approach to connecting brands with people across all channels.” Source: company website · checked Sep 5, 2026
3	Promodo Digital AgencyIndirect evidence	Lincoln, United KingdomHQ checked Sep 5, 2026	201-500	383
	“Promodo is an award-winning performance marketing agency and a reliable partner for driving measurable results in eCommerce.” Source: company website · checked Sep 5, 2026
4	ADD PeoplePartial evidence	Altrincham, United KingdomHQ checked Sep 5, 2026	201-500	292
	“We’re Add People, a team of digital marketing professionals dedicated to helping small to medium-sized businesses grow online.” Source: company website · checked Sep 5, 2026
5	BIG GroupIndirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	177
	“Founded in 1991, with offices in Amsterdam, Bath, Dubai and London our award-winning employee-owned company has consistently ranked as one of the UK's leading independent digital…” Source: company website · checked Sep 5, 2026
6	Thomson LocalIndirect evidence	Farnborough, United KingdomHQ checked Sep 5, 2026	201-500	162
	“Think Local, Think Thomsonlocal!” Source: company website · checked Sep 5, 2026
7	Investis DigitalIndirect evidence	London, United KingdomHQ checked Sep 5, 2026	501-1,000	158
	“IDX (formerly Investis Digital) specializes in elevating companies and brands and maximizing technology to build strong, relatable, and authentic connections with their audiences.” Source: company website · checked Sep 5, 2026
8	Connective3Indirect evidence	Leeds, United KingdomHQ checked Sep 5, 2026	51-200	146
	“We are a specialist performance marketing agency, and we deliver unrivalled performance for our clients on a global scale.” Source: company website · checked Sep 5, 2026
9	E IntelligenceIndirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	117
	“e intelligence is a renowned global leader in the digital marketing space.” Source: company website · checked Sep 5, 2026
10	FOUNDIndirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	104
	“We're Found, the Everysearch™ agency.” Source: company website · checked Sep 5, 2026
11	InfoserveIndirect evidence	Leeds, United KingdomHQ checked Sep 5, 2026	51-200	103
	“Let’s face it, the world has become an increasingly digital place.” Source: company website · checked Sep 5, 2026
12	The SEO WorksIndirect evidence	Sheffield, United KingdomHQ checked Sep 5, 2026	51-200	98
	“The SEO Works are an award-winning provider of search marketing, websites and paid social for leading brands and prospering SME’s.” Source: company website · checked Sep 5, 2026
13	FinixioIndirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	96
	“Finixio is UK based remote first Marketing & SEO Agency helping clients all over the world.” Source: company website · checked Sep 5, 2026
14	The Media PeopleIndirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	83
	“Powered by our people, our campaigns put your audience first.” Source: company website · checked Sep 5, 2026
15	BrainsoulsIndirect evidence	Birmingham, United KingdomHQ checked Sep 5, 2026	51-200	82
	Source: company website · checked Sep 5, 2026
16	Paramount Digital LTDIndirect evidence	St Helens, United KingdomHQ checked Sep 5, 2026	11-50	79
	“Simple.” Source: company website · checked Sep 5, 2026
17	Social BoostIndirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	79
	“Social Boost has helped to grow more than 25 million real Followers, created content for 100+ brands, and generated over 300k sales leads.” Source: company website · checked Sep 5, 2026
18	StickyeyesIndirect evidence	Leeds, United KingdomHQ checked Sep 5, 2026	201-500	77
	“Search Marketing \| Content \| Strategy Delivered by passionate people.” Source: company website · checked Sep 5, 2026
19	Blue FrontierIndirect evidence	Salisbury, United KingdomHQ checked Sep 5, 2026	51-200	76
	“Blue Frontier is a UK-based digital growth partner founded in 2005, helping organisations transform, innovate, and grow through integrated expertise in development, digital…” Source: company website · checked Sep 5, 2026
20	Mind Digital GroupIndirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	76
	“Mind Digital Group is an independent digital company that is focused on servicing global clients and partner agencies.” Source: company website · checked Sep 5, 2026
21	Century Media360Indirect evidence	Berkshire, United KingdomHQ checked Sep 5, 2026	11-50	75
	“Century Media360 will help you measure, optimize and enhance your ROI then association with us is your ultimate destination.” Source: company website · checked Sep 5, 2026
22	S4 Capital GroupPartial evidence	London, United KingdomHQ checked Sep 5, 2026	5,001-10,000	74
	“S4Capital plc is the tech-led, new age/new era digital advertising and marketing services company, established by Sir Martin Sorrell in May 2018.” Source: company website · checked Sep 5, 2026
23	KnotsyncIndirect evidence	Stafford, United KingdomHQ checked Sep 5, 2026	51-200	73
	“Leading Web Design Agency In the UK and US offering top-notch SEO, SEM, SMO, PPC, Web Design, and Development services worldwide.” Source: company website · checked Sep 5, 2026
24	GA AgencyPartial evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	70
	“GA Agency is an award-winning digital marketing agency helping brands all over the world grow their business and revenue in the online space.” Source: company website · checked Sep 5, 2026
25	MABOIndirect evidence	Middlesbrough, United KingdomHQ checked Sep 5, 2026	51-200	69
	“Unlock exceptional business growth with Mabo - an award-winning digital marketing agency specialist in paid search, social media, search engine optimisation (SEO) and Amazon…” Source: company website · checked Sep 5, 2026

Showing 25 of 7,756 online advertising agencies based in the United Kingdom

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Online advertising agencies based in the United Kingdom at a glance

As of Sep 5, 2026

1-10Median size (employees)

LondonLargest hub · 2404 HQs

2,736Contacts with mobile numbers

Sep 5, 2026Data refreshed

Companies by employee count

1-10

5,802

11-50

1,657

51-200

221

201-500

501-1,000

1,001-5,000

5,001-10,000

10001+

Verified emails by last verification

0–30

9,474

31–60

570

61–90

90–180

180+

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 online advertising agencies, so some rows will be adjacent to the category rather than pure plays. The description and evidence 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 SmartSearch, 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 “online advertising agencies”. Matching reads each company's description, not its industry code or its name.
What we exclude: Companies whose own description does not clearly place them among online advertising agencies, 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 an evidence 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, 10,114 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 5, 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.

Online advertising agencies by metro

Frequently asked

How many online advertising agencies are there based in the United Kingdom?

RevenueBase identified 7,756 online advertising agencies 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?

YELL, headquartered in Reading, tops this list with the largest team on record.

Which city has the most online advertising agencies?

London leads with 2404 headquartered companies, followed by Manchester (310) and Birmingham (201).

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 10,114 verified decision-maker contacts tracked across these 7,756 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 5, 2026.

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Online advertising agencies by geography

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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 SmartSearch, 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.