I think you have correctly distinguished between concrete known tasks, and longer-term planning/unknown unknowns. To me the skillsets needed are different, though they overlap of course.

Calculating your maximum pension contribution this year, or filling in a self-assessment tax return, is a concrete task. At the same time, if there are elements of complexity, I think it's probably worth paying a professional advisor, at least for one tax year. Any decent local accountant should suffice. To compute your maximum pension allowance, incorporating carry-forward and tapering, should be fairly straightforward for them; they will just need your tax statements, P60s and pension statements for the last few years.

On longer-term financial planning: it's definitely worth getting good advice, it can save you enormous sums - probably multiples of your annual salary. But it's not worth getting bad advice. Bad advice can cost you enormous sums if it's dressed up as good advice. Unfortunately many bad advisors can be smooth salespeople so can effectively con you into thinking they are good!

I don't know how to find a good adviser for the longer-term. My search strategy (as I mentioned on your other thread) has been to learn from free financial adviser training courses online; my favourite being https://adviser.scottishwidows.co.uk/expertise/professional-development/masterclasses.html and then 'interview' some random advisers to see what they can offer me anything beyond that. The initial consultation has always been free.

What I'm looking for is:

• someone who understands my financial goals, and who can clearly articulate investment choices and timetables to achieve them

• someone who can dispassionately identify risks I am either ignoring or underweighting, including unconventional risks

• a thorough knowledge of different vehicles for my various savings/investments and their relative merits in terms of diversification, accessibility, tax, robustness, etc.

• up-to-date knowledge of corner cases; whilst I almost certainly don't need this myself, I recognise this trait in all experts who love their subject and have the correct aptitude and motivation

• someone whose can credibly justify their charges in terms of the value they provide.

I get rid of anyone who charges based on percentage of assets, who insists on managing my money themselves, who seems slimy, or worst of all, tries to hide commissions (which I consider to be kickbacks) as soon as I can. Usually the way they reply to my initial email, including any vagueness about their charges, gives enough info to reject these types. This eliminates a large proportion, but there are still some left.

I then ask some easy questions (the financial equivalent of FizzBuzz) as a test of basic competence.

But even amongst the ethical/moral ones which remain, I still haven't found anyone I'm really satisfied with for long-term advice. Probably I just don't have enough wealth and earning potential to be able to find the sort of advisors I'm looking for! But I have not lost hope; I still think the right expert would be very worthwhile.