SaaS Marketing: Consultant or Agency in London?

I see this question pop up all the time from SaaS founders, especially around London's tech scene. You've got a bit of funding, or maybe you're bootstrapping to the next level, and you know you need to get serious about paid marketing. The problem is, the landscape is a mess of jargon. Do you need a strategic brain (a consultant) or a team of doers (an agency)?

Let's be brutally honest: most founders get this wrong. They hire an agency when they really need a consultant, burn through £20k in three months with nothing to show for it, and conclude that "paid ads don't work for us". Or they hire a consultant to run campaigns, get frustrated by the lack of hands-on execution, and end up back at square one. The truth is, both can be incredibly valuable, or a complete waste of money. It all depends on what problems you're actually trying to solve.

This isn't just another generic blog post. This is a framework for London-based SaaS founders to make the right call, based on my experience running campaigns for dozens of software companies. We're going to cut through the rubbish and give you a clear path forward.

So, what's the real difference? Aren't they just different names for the same thing?

Not at all. Thinking a consultant and an agency are interchangeable is the first mistake. It’s like comparing an architect to a construction company. You need the architect to draw up the blueprints, figure out the structural integrity, and ensure the design will actually work. You need the construction company to pour the concrete, put up the walls, and install the plumbing. Asking the construction company to design the skyscraper on the fly is a recipe for disaster. Asking the architect to lay the bricks themselves is a massive waste of their talent and your money.

A consultant is your architect. Their job is strategy. They should be helping you answer the big, painful questions:

• -> Who is our Ideal Customer Profile (ICP)? Not just demographics, but what is their career-threatening nightmare that our software solves?
• -> What's our core message that will actually get them to stop scrolling?
• -> Which channels should we even be on? Is it Google Search for high-intent users, or LinkedIn for targeting specific job titles in the City?
• -> What does our funnel look like? From ad click to PQL (Product Qualified Lead), what are the steps?
• -> How should we structure our ad accounts for scale later on?

A good consultant rarely spends their day in Google Ads or the Meta Ads Manager. They spend their time in your data, in customer interviews, and in strategy documents. They deliver a plan, a system, or a trained-up team. Their deliverable is clarity and a roadmap.

An agency is your construction company. Their job is execution and scale. You give them the blueprints (the strategy), and they build the thing. Their day-to-day is:

• -> Building and managing campaigns across multiple platforms.
• -> Writing ad copy and working with designers on creative.
• -> A/B testing everything: audiences, headlines, landing pages.
• -> Optimising bids and budgets to hit your CPA or ROAS targets.
• -> Reporting on performance and providing insights on what's working.

An agency brings a team of specialists—a media buyer, a copywriter, a strategist, an account manager. They're built for doing the work, day in and day out. Their deliverable is results, based on the strategy they're given.

You can see the problem, right? If you don't have the blueprints, the best construction company in the world is just going to build you a very expensive, very wobbly shed. If you have perfect blueprints but no one to build, you've just got a nice-looking document.

When should my SaaS hire a consultant?

Hiring a consultant is the right move in a few specific scenarios. It's almost always earlier in your journey than you think.

1. You're Pre-Product-Market Fit (or just found it)
If you're still figuring out your core messaging, your ideal customer, or your pricing, you are not ready for an agency. Pouring a big ad budget onto an unvalidated offer is like trying to accelerate with the handbrake on. A consultant will help you use a small, controlled budget for testing and validation. They’ll help you run lean experiments to find the message and audience that resonates before you even think about scaling. They help you find the 'what' and 'who' before an agency tackles the 'how many'.

2. You Want to Build an In-House Team (Eventually)
Maybe your long-term vision is to have your own team of marketing experts. A great way to start is by hiring a consultant as a fractional leader. They can create the strategy, set up the initial campaign structures, and, most importantly, help you hire and train your first marketing junior. They act as your interim Head of Marketing, ensuring your first hire doesn't spend six months learning on your dime. It’s a brilliant way to de-risk that crucial first hire. Trying to decide between building an in-house team versus hiring an agency can be tough, but a consultant can bridge that gap effectively.

3. You're Hitting a Plateau
Your in-house team is doing okay, but growth has stalled. Your CPA is creeping up, and what used to work isn't delivering anymore. A consultant can bring a fresh pair of expert eyes. They can audit your existing accounts, identify missed opportunities, and provide a strategic plan to break through the plateau. They aren't there to take over the day-to-day, but to provide the high-level strategy your team is too "in the weeds" to see.

4. You Need Highly Specialised, One-Off Expertise
Perhaps you need to crack a specific channel like LinkedIn ads for enterprise leads, or you're planning a complex international expansion. A consultant with deep, specific expertise can be brought in for a short-term project to build the strategy and maybe even run the initial pilot, before handing it over to your team or a more generalist agency. For example, if you are looking for specific expertise, you'd want to check out this expert guide to paid ads consultants.

When is hiring a SaaS marketing agency the right call?

Hiring an agency is about adding fuel to a fire that’s already burning. It's an investment in scale, speed, and expertise-at-large. Here's when to make that call.

1. You Have Product-Market Fit and a Validated Funnel
This is the absolute, non-negotiable prerequisite. You know who your customer is, you know they want what you're selling, and you have a funnel (e.g., ad -> landing page -> free trial -> conversion) that works, even if it's at a small scale. For instance, I remember one campaign for a SaaS client where we drove 5,082 software trials at just $7 per trial. But that only worked because the offer was solid. An agency's job is to take your working funnel and put it in front of tens of thousands of the right people, not to figure out if the funnel works in the first place.

2. You Have a Dedicated Budget and are Ready to Scale
Agencies aren't cheap, and they need a decent ad spend to work with to get the data they need to optimise. If you're scraping together £1k a month for ad spend, you're better off with a consultant or learning to do it yourself. But if you have at least £5k-£10k a month in ad spend and you want to deploy it efficiently for growth, an agency is your best bet. Their systems are built for managing and optimising larger budgets across multiple channels. They can turn that spend into predictable growth.

3. You Don't Have the Time or Desire to Manage It Yourself
As a founder, your time is your most valuable asset. If you're spending 10 hours a week tweaking ad campaigns instead of talking to customers or working on your product, you're making a poor trade. Hiring an agency frees you up to focus on the things only you can do. You get a team of experts managing your growth engine, with a single point of contact, for less than the price of one senior marketing hire. Wondering what that UK SaaS founder should look for in a paid ad agency? Look for one that lets you focus on your core business.

4. You Need Multi-Channel Expertise, Fast
You've maxed out Google Ads and want to expand to LinkedIn, Meta, and maybe even TikTok. Hiring individual experts for each of those is slow and expensive. A good full-service agency will have specialists in each of these areas under one roof. They can quickly launch and manage an integrated multi-channel strategy, ensuring your message is consistent and your channels are working together, not competing. This is particularly important for B2B SaaS where the customer journey often touches multiple platforms before a conversion.

The London Factor: Does being in the UK capital change the decision?

Yes, it does. The London and wider UK market has its own quirks. The competition here is fierce, especially in fintech and B2B SaaS. You're not just competing with other startups from Old Street, but with established global players who have a foothold in the City.

Costs are higher. A decent freelance consultant in London might charge anywhere from £500 to £1,500 per day. A good SaaS-focused agency in London will likely have retainers starting at £3,000 - £5,000 per month, plus a percentage of ad spend. You need to be aware of these costs going in. The higher cost of living and talent means you're paying a premium, but you're also getting access to some of the best talent in the world.

Network is everything. A London-based consultant or agency will have a deep understanding of the local ecosystem. They'll know which publications matter, which influencers have real sway, and what messaging resonates with a UK and European B2B audience. This local nuance can be the difference between a campaign that connects and one that falls flat.

I ran a campaign for a medical job matching SaaS, and we managed to reduce their Cost Per Acquisition from a painful £100 down to just £7. A large part of that was understanding the nuances of the UK healthcare job market, something an overseas agency might have missed entirely.

The talent pool is also incredibly diverse. You can find deep specialists here. If you need someone who has scaled a SaaS from £1M to £10M ARR using only Google Ads in the UK financial sector, that person probably exists and works in London. The challenge is finding them and being able to afford them.

What red flags should I look out for?

Whether you're leaning towards a consultant or an agency, there are some universal red flags you need to watch out for. Seeing any of these should make you think twice.

For Both Consultants and Agencies:

• Guaranteed Results: This is the biggest one. If anyone promises you a specific ROAS or a certain number of leads, run away. Paid advertising is not a crystal ball. There are far too many variables. An expert will talk about their process, their experience, and realistic potential outcomes based on case studies, but they will never guarantee results. It's impossible and dishonest.
• Lack of Relevant Case Studies: If you're a B2B SaaS and they only show you case studies for eCommerce fashion brands, they are not the right fit. You need to see that they have solved similar problems for similar businesses. I'm not saying they need to have worked with your direct competitor, but they need to understand your business model. For instance, our experience scaling a B2B SaaS to 4,622 registrations for $2.38 each is highly relevant to other software companies.
• Jargon-heavy Sales Pitches: If they spend the whole call talking about "synergies," "leveraging platforms," and "growth hacking" without talking about your specific business problems, they are hiding a lack of substance. A true expert makes complex things simple. They should be asking you more questions than you ask them.
• One-Size-Fits-All Approach: If they present a rigid "package" without first doing a deep dive into your business, they are a factory, not a partner. Every SaaS is different, and the strategy should be bespoke.

Specific to Agencies:

• Long, Inflexible Contracts: A 12-month mandatory contract from day one is a huge red flag. A confident agency will often start with a 3-month trial period to prove their value. They know that if they perform well, you'll want to stay.
• Junior Account Managers: Ask who will be working on your account day-to-day. Often, you'll be sold by the senior partner, then handed off to a junior who is fresh out of university. You want to know the level of experience of the person who will actually be in your ad accounts.
• Lack of Transparency: You should have full ownership and access to all your ad accounts. The data is yours. If an agency runs ads through their own account and just sends you a PDF report, you have no visibility and no control. This is a massive no-no.

Specific to Consultants:

• The "Career Consultant": Be wary of consultants who have never actually worked "in the trenches" at a company. The best consultants have been where you are—they've been the Head of Marketing, they've managed the budgets, they've answered to a CEO. They have operational experience, not just theoretical knowledge.
• Focus on Execution over Strategy: If a consultant seems more eager to get into your ad accounts and start tweaking bids than to talk about your ICP and LTV, they're not a consultant; they're a freelancer. You're paying them for their brain, not just their hands. The whole point of hiring a consultant is to get strategic direction, something we explore in depth in our UK founder's guide on this exact topic.

So, what's my final recommendation?

There's no single right answer, but there is a right process to find your answer. It's about being brutally honest about what stage your business is in and what problem you're truly trying to solve.

Don't hire an agency to fix a strategy problem. Don't hire a consultant to do the day-to-day work of a full team. I've put together a summary table to make the choice as clear as possible.

This is the main advice I have for you:

Ultimately, the choice between a consultant and an agency is a reflection of your company's maturity. Making the right one at the right time can be the difference between stagnating and hitting your next growth milestone. Get it wrong, and you'll join the long list of founders who mistakenly believe paid ads "just don't work".

If you're still unsure where you fall, or you'd like a second opinion on your current strategy, this is exactly what we help founders with. We offer a free, no-obligation strategy session where we can look at your business and give you an honest assessment of what you need right now. It might be us, it might be a consultant, or it might be that you're not ready for either. But you'll leave the call with clarity.