uneekSTYLA
Noticed on your Cadred thread you were considering a part build if it was easy enough.
A few weeks ago I was in pretty much the same boat as you, considering a pre-built as I have little experience putting PC's together. Everyone has however talked me round in to doing a part build. I'm putting it together as we speak and, although it's a little fiddly, there's so many guides and videos on youtube of my exact components that it makes the process so much easier.
If you're interested this is what I put (or am putting) together for £640:
I5 2500k @ 3.4GHZ (Will OC to 4.2-4.5)
8gb Corsair Low Profile RAM
Arctic i30 Cooler
MSI 560ti 448 Core 1280mb
MSI P67A-GD53 Mobo
500GB Seagate HDD
CM690 Case + 650W CM PSU
WIFI Card
Sony CD/DVD-RW drive
You can easily shave £50 off that price if you were to go for a cheaper motherboard such as a ASUS P8H61-MLE USB3 and drop the wifi card. Remember however that with a 2500k it will only overclock with a p67 or a z68 motherboard from what I have read, therefore that cheaper H61 motherboard will [b]not[/b] let you overclock to a decent degree.
If you're interested I can link you to the sites where I found the components at the cheapest prices.