UK Founder's Guide to Hiring Paid Ads Agencies

I get it. You're a founder in the UK, you've got a limited budget, and every agency website you visit claims to be the 'best', 'award-winning', or a 'leading partner'. It’s an absolute minefield of jargon and vague promises, and you're trying to figure out who to trust with your hard-earned cash without getting burned. The truth is, most of the advice out there is rubbish.

The whole idea of a single "best" paid ads agency is a myth. It doesn't exist. What does exist is the right agency *for you*—for your specific business model, your industry, your budget, and your stage of growth. This guide is going to give you a no-nonsense framework for finding that agency. Forget the awards and the slick sales pitches. We're going to focus on what actually drives results and how to spot genuine expertise from a mile off.

So, what actually matters when you're looking for help?

When you strip away all the sales talk, vetting an agency comes down to just a few core things. If you get these right, you massively de-risk your investment. Most founders get distracted by fancy offices in Shoreditch or impressive client logos from five years ago. Don't make that mistake.

First up, case studies. But not just any case studies. You need to see proof that they've solved a problem similar to yours, for a business similar to yours. Are you a B2B SaaS company? Then a case study about a local eCommerce sock brand is utterly useless to you. I've run campaigns for B2B SaaS clients where we've got their CPL down to $22 on LinkedIn, and others where we've generated over 1500 trials on Meta. That’s specific, relevant proof. If an agency can't show you something similar for your sector, they're probably going to be learning on your dime. And you cant afford that.

Look for the numbers. How much revenue was generated? What was the Return on Ad Spend (ROAS)? What was the Cost Per Acquisition (CPA)? If the case study just talks about "increased brand awareness" or "millions of impressions," it's a red flag. I remember one campaign we ran for a luxury brand that got 10 million views, which sounds great, but for most businesses, that's a vanity metric. What you want is results that effect the bottom line. For an ecommerce client selling cleaning products, we hit a 633% return and increased their revenue by 190%. That’s a number you can take to the bank.

Here’s a simple flowchart to help you cut through the nonsense when you're looking at a case study:

The second test is the discovery call. This is where you find out if they're actually experts or just good at sales. A good agency will spend most of the call asking *you* questions. What's your average revenue per customer? What's your profit margin? What's your sales cycle? They're trying to understand your business economics. A bad agency will spend the whole call talking about themselves, their 'proprietary process', and how great they are. If they promise you a specific result, like a "guaranteed 5x ROAS," end the call. No one can promise that. Tbh in paid advertising, it's impossible to predict exactly how ads will perform. Anyone who tells you otherwise is either lying or inexperienced. What you're looking for is a strategic partner, not a yes-man.

Lastly, look at their reviews and social proof. Are the reviews detailed? Do they talk about specific challenges and how the agency helped solve them? Vague, one-line reviews are often not that helpful. Dont get too hung up on where they are based, a remote agency with deep expertise in your niche is a million times better than a local one that doesnt have a clue.

What homework do you need to do first?

Here's the bit that most founders skip. You can't effectively hire an agency if you don't know your own numbers. The single most important metric you need to understand is your Customer Lifetime Value (LTV). This number tells you what a customer is worth to your business over their entire relationship with you. Once you know your LTV, you can figure out how much you can afford to spend to acquire a customer (your Customer Acquisition Cost, or CAC).

An agency that doesn't ask you for this number on the first call probably isn't worth your time. A great agency will help you think through it. Here's the basic maths:

LTV = (Average Revenue Per Customer * Gross Margin %) / Monthly Churn Rate

Let's break it down with a realistic UK example. Imagine you run a subscription box service.

• -> Average Revenue Per Customer (per month): £30
• -> Gross Margin: 60% (after cost of goods, shipping etc.)
• -> Monthly Churn Rate: 10% (you lose 1 in 10 subscribers each month)

Your LTV would be (£30 * 0.60) / 0.10 = £180. Each subscriber is worth £180 in gross margin to you. A healthy LTV:CAC ratio is about 3:1. This means you can afford to spend up to £60 to acquire a new subscriber and still have a very profitable business. Suddenly, seeing a £40 CPA from your Facebook ads doesn't seem so scary, does it? It looks like a bargain. This is the maths that unlocks scalable growth.

To make it easier, here's an interactive calculator. Play around with your own numbers to see what you can afford to spend.

The other peice of homework is to properly define your customer. And I don't mean "women aged 25-40 who live in London." That's useless. You need to define them by their pain. What is the urgent, expensive, career-threatening nightmare that keeps them awake at night? Your product or service is the aspirin for that headache. For example, if you sell compliance software to FinTechs, your customer isn't 'Head of Operations'. It's 'a Head of Ops who is terrified of a surprise audit revealing a GDPR breach that could cost the company millions and get them fired'. When you understand that, you know exactly what message will get their attention.

What sort of costs are realistic for the UK market?

This is the million-dollar—or rather, million-pound—question. Costs vary wildly, but there are some general benchmarks we see across the campaigns we run. A lot of founders come to us with completely unrealistic expectations about ad costs in the UK. Understanding the potential investment will help you have a much more productive conversation with any prospective agency.

First, let's talk about lead and signup costs. For things like newsletter signups, free trial registrations, or simple lead form fills, you're competing for attention but the user commitment is low. Based on our experience, in a developed market like the UK, you should probably budget for a Cost Per Click (CPC) somewhere between £0.50 and £1.50. From there, a decent landing page should convert between 10% and 30% of that traffic. So, the maths looks like this:

• -> Worst case: £1.50 CPC / 10% conversion rate = £15 per lead/signup.
• -> Best case: £0.50 CPC / 30% conversion rate = £1.67 per lead/signup.

The reality for most campaigns starting out will be somewhere in the middle. If an agency tells you they can get you leads for 50p from day one, be very skeptical. We've managed to get signups for an events app for under £2, but that was after significant testing and optimisation.

When it comes to actual sales for an eCommerce business, the numbers change dramatically. The user commitment is much higher, so conversion rates are naturally lower, typically between 2% and 5%. Using the same CPCs:

• -> Worst case: £1.50 CPC / 2% conversion rate = £75 per purchase.
• -> Best case: £0.50 CPC / 5% conversion rate = £10 per purchase.

Obviously, if you're selling a £20 t-shirt, a £75 acquisition cost is a disaster. If you're selling a £500 piece of equipment, it's a huge win. This is why knowing your margins and LTV is so important. You shouldnt just focus on the Cost Per Purchase though; what really matters is the Return On Ad Spend (ROAS). For one of our clients selling maps, we generated $71k in revenue at an 8x ROAS. That's the goal.

To give you a visual idea, here’s how those cost ranges stack up against each other.

On top of the ad spend, you'll have the agency's fee. This is usually a monthly retainer, a percentage of ad spend, or a combination of both. For a startup or small business, expect to pay a retainer of at least £1,500 - £5,000+ per month for a competent agency or consultant. If someone quotes you £500, they're either desperate, inexperienced, or they're going to outsource it to someone even cheaper. You get what you pay for. Remember, a good agency isn't a cost centre; they are a growth investment. Paying a bit more for genuine expertise that can deliver a 6x ROAS is infinately better than paying less for an agency that burns your ad budget and gets you nowhere. If you're serious about growth, you can also explore how to find the right freelance talent to manage your ads.

How to spot the cowboys and avoid getting ripped off

The UK market is flooded with agencies, and sadly, a lot of them are not very good. They're great at selling, but not so great at delivering. Here are the biggest red flags to watch out for. If you see any of these, you should probably walk away.

1. Long-Term Contracts: If an agency tries to lock you into a 12-month contract from day one, it’s a massive red flag. Why? Because they aren’t confident they can deliver results that will make you want to stay. A good agency will be happy with a 3-month initial term or even a 30-day rolling contract. They know that if they do a good job, you won't leave.
2. They Own the Ad Account: This is a non-negotiable. You, the client, must ALWAYS own your ad accounts (Google, Meta, LinkedIn, etc.). The agency should be granted access as a partner or manager. If the agency sets up the account under their own name, they hold all your data and campaign history hostage. If you leave, you start from scratch. It's a shady tactic used to create lock-in.
3. Guaranteed Results: As mentioned before, anyone who guarantees a specific ROAS or number of leads is lying. The ad market is an auction, and performance depends on dozens of factors outside of an agency's control, including your offer, website, pricing, and competition. An expert will talk about realistic targets and a strategy for testing and optimisation, not impossible guarantees.
4. Vague, Fluffy Reporting: Their monthly report should be focused on the metrics that matter to your business: leads, sales, cost per acquisition, and return on ad spend. If their reports are full of vanity metrics like impressions, reach, clicks, and click-through rate (CTR) without connecting them to bottom-line results, they're likely trying to hide poor performance.
5. The Bait and Switch: This is a classic. You'll have your sales calls with a senior, experienced director who sounds brilliant. You sign the contract, and then your account is handed off to a junior account manager who is fresh out of university and learning on the job. Always ask who, specifically, will be working on your account day-to-day and what their level of experience is.

Making the wrong choice can be costly, not just in wasted fees and ad spend, but in the opportunity cost of months of no growth. That’s why a careful vetting process is so important. For founders looking to take the next step, our guide on hiring a paid ads agency in the UK provides an even deeper framework.

The Final Checklist: Your Action Plan

Alright, that was a lot of information. To make it simple, I've boiled it all down into a final action plan. Use this table as a checklist when you're talking to potential agencies. It summarises the key points we've covered and will help you make a logical, data-driven decision rather than an emotional one.

This is the main advice I have for you:

So, should you hire an agency?

After all this, you might be wondering if it's worth the hassle. The answer is: it depends. If you're just starting out with a tiny budget, you might be better off learning the ropes yourself or hiring a freelancer. But if you have a proven offer, you know your numbers, and you're ready to invest properly in growth, the right agency can be an absolute accelerant for your business. The difference between an average campaign and a great one isn't a 10-20% improvement; it can be the difference between burning cash and building a multi-million-pound business.

The right partner brings years of experience, a deep understanding of what works across hundreds of accounts, and a strategic perspective that you're too busy to have when you're running the business. They can help you avoid the costly mistakes most founders make and get to profitability faster. Choosing the right path can be tough, which is why we've put together a full breakdown of the DIY vs Agency decision for UK founders.

If you've read this far, you're already ahead of 90% of business owners looking for help with their advertising. You know what to look for, what questions to ask, and what red flags to avoid. If you've done your homework and are looking for a team of specialists to help you scale, you might be ready for expert help.

We offer a completely free, no-obligation strategy consultation. We’ll take a look at your business, your goals, and what you've tried so far, and give you honest, actionable advice on what we'd do next. It’s not a sales pitch in disguise; it’s a genuine chance to get expert eyes on your project. If we think we're a good fit to help, we'll tell you. If not, we'll tell you that too, and point you in the right direction. Feel free to book one in if you think it would be helpful.