First hundred pounds: measurement
Analytics installed, conversions defined, call tracking if the phone matters. Unmeasured marketing isn't marketing, it's donation. This costs almost nothing but discipline, and it makes every later pound accountable.
The next thousand: a site that converts
Not a brochure. A fast site that says what you do, for whom, at what price, with proof and a clear next step. Plus a complete Google Business Profile if you serve Sheffield locally. This is the machine every other channel feeds. A weak site taxes everything upstream of it.
Then: capture existing demand
If people already search for your thing, tight Google Ads and local SEO come first: highest intent, fastest feedback. If nobody searches for it yet, skip ads and spend the time building an email list and content where your buyers already gather. Demand capture before demand creation, always.
Only then: scale and experiment
Once one channel returns predictably, feed it until it bends, then add the next. The startup graveyard is full of businesses running six channels at £200 each. One channel at £1,200, run properly, teaches you something and might just pay for itself.