Three things are genuinely worth paying for early, and the rest can usually wait.
An accountant, for anything with a filing deadline or a tax consequence — and for the judgement calls that are expensive to unwind, like share structure and how you pay yourself. Ours is quoted in about two minutes, and every specialist price is published rather than quoted on request.
A solicitor, for your shareholders—’ agreement and any contract that carries real risk. Template documents are fine for the ordinary things and a false economy for the round that matters.
Insurance, including employers—’ liability the moment you have a first employee, which is a legal requirement rather than a judgement call.
What is usually not worth paying for at the start: business plan writing services, most —“grant finding—” subscriptions, and anyone charging a percentage of a tax relief you were entitled to anyway.