When I got my PC I looked around for the components I wanted, and then went looking for a company that would let me build my own to that approximate specification. I found one that was reasonably priced, and had the parts I wanted. And was impressed by the speed of turnaround, and how good their customer service was. Heck, they had a page that showed you how long the live waiting times were on their phones so you knew when it was worth calling (not that I ever saw them go over five minutes).
Today, helping my father look for a new PC (because he hates his children having better computers than him), I decided to check the PC Pro Reliability & Service awards for 2009 and
discovered that the winner was the people I'd gone with -
PC Specialist.
So, should you be buying a PC (and be based in the UK) then I have no hesitation in recommending them.