Jeremiah Harbottle coughed up some electrons that declared:

Right.
I'm planning to upgrade - my current PC is 4 years old and exhibiting
behavioural problems.

I'd like to just be able to order the main bits (M/Board, CPU, Case, etc)
and get them assembled and sent on to me - (For various reasons, I don't
want to fiddle about doing it myself...)

Anyone recommend any online vendors that offer this sort of service?

You might be better off going to a traditional computer shop (not PC World)
on the High Street - those are the sort of people who are likely to manage
this.

Cheers

Tim