Accountants ARE helpful.

But are you paying him for advice you could (with help from the HUGE amount of tax advice websites) get yourself and do the self assessment thang?

That's a lot of effort for most especially if their time is previous to them i.e. self employed or working in a very lucrative sector where long hours are essential. An accountant, if you can afford it, will make getting the most out of your money a lot easier.