London's Ultimate Guide To Hiring A Paid Ads Agency

I get it. Trying to find a good paid ads agency in London feels like wading through a swamp. Every website looks the same, full of buzzwords and slick promises. They all claim to be "data-driven" and "results-focused", but when you try to figure out who's actually any good, it's a nightmare. You're right to be overwhelmed.

The truth is most agencies are better at marketing themselves than they are at marketing their clients. They sell you a dream, not a viable strategy. But there are good ones out there, you just need a better filter to find them. So forget the sales pitches for a minute. I'm going to give you a no-BS framework for cutting through the noise and finding a partner who can actually help your business grow, based on my years of running campaigns for all sorts of companies.

Forget the Slick Pitches, Demand Proof: Are Their Case Studies Real?

First thing's first. Before you even think about booking a call, you need to become obsessed with one thing: their case studies. An agency’s website is marketing fluff; their case studies are the closest thing you'll get to a CV. If they're buried, hard to find, or vague, that's your first red flag.

But just finding them isn't enough. You need to dissect them. What are you looking for?

-> Relevance. Have they worked with businesses like yours? If you're a B2B SaaS founder in the fintech space, a case study about a local dog grooming business is pretty much useless to you. I've run loads of campaigns for B2B software companies, and the challenges are completely different. For one client, we hit a $22 Cost Per Lead targeting decision makers on LinkedIn. For another, we reduced a £100 CPA down to just £7. Those are the kind of specific, relevant results you want to see. If they don't have your exact niche, are their results at least in a similar field with similar challenges?

-> Real Metrics. Are they bragging about "10 million views" or a "huge jump in engagement"? Honestly, who cares. These are vanity metrics. Views don't pay the bills. You need to see business metrics. Revenue generated. Return On Ad Spend (ROAS). Cost Per Acquisition (CPA). I remember one campaign for a prize draw company where we generated £107k in revenue at a 618% ROAS. That's a real number that means something to a business owner. If their case studies are full of fluff and lack hard numbers in pounds and pence, they're probably hiding poor performance.

-> Honesty. A good case study isn't always a perfect story of instant success. Sometimes it shows a problem, a test, and a solution. That shows they can think on their feet. Any agency that claims every single campaign is a wild success from day one is not being straight with you.

Tbh, if an agency can't show you a portfolio of detailed, relevant case studies with real financial metrics, your conversation with them should be over. They are essentially asking you to pay them to learn on your dime. If you're struggling to figure out what to look for, our guide on vetting agencies in London goes into more detail on this.

What Questions Should I Ask on the Intro Call to Expose an Amateur?

Alright, so you've found an agency with some promising case studies. The next step is the "intro call" or "free consultation". This is where you turn the tables. This is not a sales pitch for them; it's a job interview, and you're the hiring manager. Your goal is to see if they actually have the expertise they claim to have.

Don't let them run the show with a canned presentation. Interrupt them. Ask hard questions. Here are a few of my favourites to seperate the experts from the chancers:

"Based on what you know about my business, what ad platform would you start with and why?"
This is a basic test. A bad answer is "Oh, we'd do Google and Facebook, they're the best." A good answer is considered. They should ask you questions back. "Well, who is your ideal customer? Are they actively searching for a solution right now? If so, Google Search is probably our starting point. If not, we might need to look at generating demand on a platform like LinkedIn or Meta, but the targeting would need to be very specific." Their reasoning tells you everything.

"What would your initial 30-60 day plan look like for us?"
Red flag: "We'll get you a 5x ROAS in the first month!" A real expert will talk about a methodical process. Something like: "Week 1 is all about deep research into your customers and competitors, and a technical audit of your tracking setup. Week 2 we'd build out initial campaign structures and creative. We'd aim to launch in week 3, and the rest of the first month would be about gathering data, not immediate profit. We need to see what's working before we can scale." It sounds less exciting, but it's realistic.

"What's the biggest mistake you see companies in my industry making with their ads?"
This probes their niche expertise. If they give a generic answer like "not having a good landing page," they don't know your world. A B2B agency should be able to say, "For high-ticket services like yours, too many firms in London try to go for a hard sell straight away. The sales cycle is longer. We'd focus on a lower-friction offer first, like a strategy guide or a webinar, to build trust before asking for a sales call." This shows they've been around the block.

"Walk me through a campaign that *didn't* work initially and tell me how you fixed it."
This question is brilliant. It tests for honesty and problem-solving skills. Everyone has campaigns that fail. The amateurs will get flustered or pretend it's never happened. The pros will see it as a chance to show off how they think. They'll talk about analysing the data, forming a hypothesis, and systematically testing variables until they turned it around. This is what you're actually paying for.

Agency Fees in London: Are They Ripping Me Off?

This is the big one, isn't it? Pricing can feel totally arbitrary. You'll get quotes from £1,000 a month to over £10,000, and it's hard to know what's fair. The reality is, you're paying for expertise, time, and the overheads that come with running a business in London. Let's break down the common models.

-> Monthly Retainer: This is the most common. You pay a fixed fee each month for the agency to manage your campaigns. In London, for a good quality small agency or an experienced consultant, you're likely looking at a starting point of £1,500 - £4,000 per month. The big, well-known agencies in places like Shoreditch can easily be £8,000+ a month. This model is predictable, but make sure the scope of work is very clear.

-> Percentage of Ad Spend: Here, the agency takes a cut of what you spend on ads, usually 10-20%. This can be good as it incentivises them to scale your spend, which should mean you're getting results. The downside is that it can also incentivise them to just spend your money, whether it's profitable or not. This is more common for larger ad budgets (£20k+/month).

-> Performance-Based: This sounds great in theory – "you only pay for results!" – but it's rare and often has strings attached. The agency might take a percentage of revenue or a fee per lead. The problem is it creates a conflict. The agency is incentivised to go after the cheapest, lowest-quality leads to hit their numbers, which might not be the right customers for you. Most reputable agencies avoid this model because of how easily it can be gamed.

Here's the contrarian truth about pricing: the cheapest agency is almost always the most expensive one in the long run. A £1,000/month agency that wastes £5,000 of your ad spend is far more costly than a £3,000/month agency that turns that same £5,000 into £25,000 of revenue. Don't focus on the fee in isolation. Focus on the potential return. You can use our guide to agency pricing and ROI to understand this better. A good agency isn't a cost; it's an investment in a profit-generating engine for your business.

Should I Hire a Specialist or a 'Do-it-All' Agency?

London is packed with agencies, and they often fall into two camps: the specialists and the generalists. The generalists will happily take on any client, from a law firm to an eCommerce brand to a SaaS company. The specialists focus on a specific industry or business model.

My take? For most businesses, especially B2B, a specialist is almost always the better choice. Think about the London market. It's heavily weighted towards finance, professional services, and tech (around Silicon Roundabout and the City). These are complex industries. A generalist agency might understand how to run a Facebook ad, but do they understand the mindset of a Chief Financial Officer you're trying to reach? Do they know the difference between a MQL and a SQL? Do they grasp the long, complex sales cycles involved?

Probably not. A specialist B2B ad agency in London lives and breathes this stuff. They already know which platforms work (hint: it's often LinkedIn, where, as I talked about, we've hit CPLs around the $22 mark for decision makers), what messaging resonates, and what offers will actually get a response. They don't have to learn your industry on your budget.

For eCommerce or simpler B2C services, a good generalist agency with deep platform expertise on Meta and Google can be a great option. I remember one eCommerce client where we achieved a 1000% ROAS on Meta ads. But even then, I'd look for one that has at least some experience with your product type. An agency that's great at selling £20 t-shirts might not have a clue how to market a £2,000 piece of home-gym equipment. Expertise matters.

They Look Good, But What About the Contract? And References?

So you've done your due diligence. You've found an agency with great, relevant case studies. They aced your interview questions on the intro call. The price feels right for the value. You're almost there. Just the final details to sort out.

First, the contract. Don't just sign it. Read it. You're looking for a few key things. Is the scope of work clearly defined? What exactly are they going to do each month? How often will they report, and what metrics will be in that report? Most importantly, what's the commitment? I'd be very wary of any agency that tries to lock you into a 12-month contract from day one. A 3-month initial term, followed by a monthly rolling contract, is much fairer. It gives you an out if things go sour and keeps them motivated to perform.

Now, about references. This is where my view is a bit contrarian. Many people will tell you to ask for references to speak to their current clients. Tbh, if a potential client asks us for references after they've reviewed our detailed case studies and we've given them a free, in-depth strategy review, it's a bit of a red flag for us. It signals a fundamental lack of trust from the very begining. We've already shown them our work and given them our expertise for free. A top-tier agency's proof should be in their public results and the value they provide upfront. Asking to take up the time of their happy, paying clients feels unnecessary and suggests that the trust required for a good partnership isn't there. It's a two-way street, after all. If the public proof isn't enough, it might not be the right fit. Learning how to properly assess an agency is more about evaluating their work than talking to their clients.

I've detailed my main recommendations for you below:

Hiring an agency is a big decision, and it's easy to get it wrong. But by following this framework, you're no longer just guessing. You're making an informed decision based on evidence, expertise, and a clear understanding of value. You're not just looking for a supplier to click buttons; you're looking for a strategic partner who can help you navigate the complexities of paid advertising and drive real, measurable growth for your business.

If you've gone through this and are still struggling, or you just want an expert second opinion on your current strategy, it might be worth getting some professional help. We offer a free, no-obligation strategy consultation where we can take a look at your specific situation and give you some actionable advice. It's often the best way for founders to see the level of expertise they could have working on their business.