UK Paid Ads Agencies: The Founder's Vetting Guide

I see this all the time. A founder in the UK decides they need to hire a paid ads agency. So they do what any sensible person would do: they open a spreadsheet. They list a dozen agencies, with columns for location, team size, awards, maybe even their hourly rate. They spend weeks comparing sales decks and polished websites. And in the end, they almost always make the wrong choice.

Let's be brutally honest. That entire process is a complete waste of time. It’s a box-ticking exercise that tells you absolutely nothing about the one thing that will determine your success: the quality of the thinking you're about to hire. You're not buying a commodity; you're investing in a strategic partner whose decisions will directly impact your cash flow. Comparing agencies like you're buying office supplies is the fastest way to burn through your marketing budget with nothing to show for it.

The real way to compare paid advertising agencies in the UK isn't about their post code or how many awards they have gathering dust in their office. It's about rigorously vetting their experience, their strategic approach, and their ability to prove—with hard numbers—that they can solve problems like yours. This is a guide on how to do just that.

So, your agency shortlist is probably rubbish. Why?

Most founders build their initial list of potential agencies based on vanity metrics. They see a slick website, an office in a trendy part of London or Manchester, and a client list that includes a few recognisable names. They're impressed by the sales pitch from a charismatic director. None of this matters.

A big team doesn't mean you'll get their best people. Often, the opposite is true. The senior partners handle the sales calls, and once the contract is signed, your account is handed off to a junior account manager juggling ten other clients. Those awards? They’re often pay-to-play industry back-patting exercises. And that big-name client they worked with? They might have just been responsible for a tiny fraction of a massive budget, a completely different challenge to growing a startup or SME from the ground up.

You have to shift your mindset. You're not hiring a company. You are hiring the specific brain of the person or small team who will be in your ad accounts every day. Your entire vetting process should be focused on one question: is this person a genuine expert who understands my business, or are they just following a generic playbook? Getting this right is about understanding the subtle differences between the agencies that talk a good game and the ones that actually drive performance.

The first, and most important, place to look for evidence is their track record.

Can they actually prove they're any good?

Forget the testimonials on their homepage. The only currency that matters in this game is case studies. But not all case studies are created equal. Most are marketing fluff, designed to obscure rather than inform. You need to learn how to dissect them like a detective looking for clues.

A weak case study says something like: "We helped a leading fashion brand increase brand awareness by 200%." This is meaningless. What does "brand awareness" even mean? How was it measured? It’s a classic sign of an agency that can't point to real business impact.

A strong case study, on the other hand, is specific and quantifiable. For example, one campaign we worked on for a women's apparel brand delivered a "691% Return". It immediately gives you a hard metric (ROAS) and the niche. Or for a software client, we "Reduced £100 CPA (Cost Per User Acquisition) to £7 CPA". This shows a clear "before and after" and demonstrates a deep understanding of a key SaaS metric. This is the level of detail you should be looking for. It shows they track what matters and have experience delivering tangible results, in your currency (£).

Here's a simple framework to analyse an agency's case studies:

If an agency can't show you at least one or two strong case studies that are relevant to your business model (e.g., B2B SaaS, eCommerce, lead gen), then they are asking you to pay for their education. Don't do it. Walk away. This is the single most important filter in the entire process of hiring a paid ads agency in the UK.

The Free Consultation is Your Ultimate Litmus Test

Every half-decent agency will offer a free initial call or consultation. Most founders treat this as a chance for the agency to pitch them. This is a mistake. You need to flip the script. This isn't a sales pitch; it's the final round of your interview process. It's your one chance to get past the marketing polish and assess the quality of their thinking in real-time.

Don't let them control the conversation with a slide deck. Come prepared with specific, strategic questions about your business:

• -> "Looking at my website, what's the single biggest weakness you see for converting paid traffic?"
• -> "We sell to [your ICP]. Based on your experience, would you prioritise LinkedIn or Google Ads for us in the first three months, and why?"
• -> "What's the most common, costly mistake you see businesses in our industry making with their ads?"
• -> "What key metrics would you focus on for us in the first 90 days to determine if the campaigns are working?"

What you're listening for isn't a perfect, pre-prepared answer. You're listening for how they think. A good partner will be curious. They'll ask you clarifying questions about your margins, your customer lifetime value, and your sales cycle. They'll give you a direct, honest opinion, even if it's not what you want to hear. They might even tell you that paid ads aren't the right move for you right now. This is a massive green flag – it shows they prioritise client success over their own revenue.

A bad partner, a salesperson in disguise, will give you vague, generic answers. They’ll talk about "our proprietary process" or "a multi-channel synergistic approach." They’ll promise the world. "Oh yes, we can definitely get you a 10x ROAS." Tbh, nobody can promise specific results in paid advertising. There are too many variables. Anyone who gives you a guarantee is either lying or naive. Run away. This call is your best chance to understand not just what they do, but how much it might cost and what value you'll get, which is a key part of understanding the true cost and ROI of hiring an agency.

Does a London Agency Beat a Manchester Maven? The Location Myth

A lot of founders, particularly in the South East, get fixated on hiring a London-based agency. There's a perception that the best talent must be concentrated in the capital. While there are some excellent agencies in London, this mindset is outdated and limiting. In 2024, your agency's postcode is one of the least important factors in your decision.

You are hiring for niche expertise, not proximity. Would you rather have a generalist agency down the road in Shoreditch who has never run a campaign for a B2B SaaS company before? Or a specialist in Bristol, Leeds or Edinburgh who has a portfolio of case studies showing they've scaled five different SaaS businesses just like yours? It's a no-brainer.

The tools we use—Google Ads, Meta, Slack, Loom—are all remote. Communication is seamless. Strategy sessions can be more focused and productive over video call than in a stuffy boardroom. Unless you run a hyper-local business that requires an agency to have an intimate, on-the-ground knowledge of your specific neighbourhood, there is very little advantage to hiring locally.

By dropping the location constraint, you open up the entire UK talent pool. This allows you to focus on what actually matters: finding a team with proven, repeatable success in your specific sector. Don't let geography dictate a critical business decision. If you are set on a London agency, at least make sure you're following a solid process for properly vetting London-based paid ad firms to separate the experts from the pretenders.

The Interactive Agency Vetting Scorecard

To make this process more objective, I've put together a simple interactive tool. Use this during or after your consultation calls to score each agency you speak with. It forces you to look past the sales pitch and focus on the signals that actually correlate with success.

This simple exercise will quickly separate the serious contenders from the charlatans. An agency that scores highly across these areas is one that respects your business, has a track record of success, and is transparent in its dealings. They are far more likely to become a valuable long-term partner than one that just has a flashy website.

The Final Details: Contracts, Pricing, and Getting Started

Once you've found an agency that passes the sniff test, you're onto the final details. Don't switch off your critical brain here. The way an agency handles contracts and pricing tells you a lot about them.

In the UK, you'll typically see a few pricing models:

• Monthly Retainer: A fixed fee each month. Simple and predictable. This is very common.
• Percentage of Ad Spend: The agency takes a cut of what you spend on ads. This can incentivise them to scale your spend, which isn't always the right move. Be wary of this if you're not a massive spender.
• Performance-Based: A lower retainer plus a bonus for hitting certain targets (e.g., a fee per lead or a percentage of revenue). This can be great as it aligns incentives, but make sure the targets are realistic and clearly defined.

The model itself is less important than the transparency. They should be able to clearly explain their fees and what you get for them. If it feels confusing or they're cagey about the details, it's a red flag. When it comes to deciding if hiring an agency makes financial sense over going it alone, it's worth weighing the pros and cons of DIY vs agency paid ads management carefully.

As for the contract, here are the non-negotiables:

• You own the ad accounts. Always. The agency should work within accounts that you own and have full admin access to. If they insist on running ads through their own accounts, walk away immediately. You want to retain all your data and campaign history if you part ways.
• A reasonable notice period. A 30-day notice period is standard. Anything longer, like 90 days, is a sign they lack confidence in their ability to retain clients through good performance.
• Clear reporting standards. How often will they report to you, and what will those reports contain? It should focus on the business metrics you agreed upon, not a data dump of vanity metrics.

Hiring an agency is just the first step. To get the most out of the relationship, you need an effective management process in place. For more on this, we've put together a guide on the founder's framework for managing agencies for maximum ROI.

My main recommendations for you are below:

Choosing the right paid ads agency is one of the most significant marketing decisions you'll make. Getting it right can transform your business's growth trajectory. Getting it wrong can be an incredibly expensive and frustrating mistake. Ditch the spreadsheet and the superficial comparisons. Focus your energy on this proven framework instead.

Ultimately, this isn't just about finding someone to press buttons in an ad platform. It’s about finding a partner who can provide strategic counsel, challenge your assumptions, and act as an extension of your growth team. They save you from costly trial-and-error and bring years of experience to the table from day one. By following this framework, you dramatically increase your chances of finding a UK agency that doesn't just manage your spend, but multiplies your investment.

If you'd like to experience the kind of strategic consultation we've described here, we offer a completely free, no-obligation strategy session. We'll review your current efforts, answer your toughest questions, and give you honest, actionable advice you can use, whether you decide to work with us or not.

Hope this helps!