from pc world, i'd get a mac EDIT: For off the shelf system Evesham are sposed to be pretty rock solid from the computer active reviews I have read.
Dell. Cheap, cheerful, good value for money. (Provided you're not wanting a gaming machine). Have you thought about building your own? It's a lot cheaper, and a good experience.
Evesham & Dell seconded. Also consider anything A-Listed or recommended in PC-Pro, such as Mesh, Hi Grade etc... CJM
I thought Time went bust? If they are still around, I'd avoid them like the plague - I've lost count of the number of times I've heard bad things about them (they appeared on 'Watchdog' god-know how many times). I'd go with Dell, Evesham or Scan if I were you. Steer clear of PC World, they're a bunch of monkeys!