I still think you should wait till the end of the month and to be honest £600 would be a much better budget to spec around. However i will take up the challenge now as so many others have
YOUR BASKET
1 x
VTX3D HD 7850 2048MB GDDR5 PCI-Express Graphics Card with FREE Dirt3 PC Game £179.99
1 x
Intel Core i3-2120 3.30GHz (Sandybridge) Socket LGA1155 Processor - Retail £99.95
1 x
Gigabyte Z68AP-D3 Intel Z68 (Socket 1155) DDR3 Motherboard REV 1 £84.98
1 x
BitFenix Shinobi USB3.0 Gaming Case - Black £46.98
1 x
OCZ ZS Series 550W '80 Plus Bronze' Power Supply £43.98
1 x
Kingston HyperX Genesis Grey 8GB (2x4GB) DDR3 PC3-12800C9 1600MHz Dual Channel Kit (KHX1600C9D3X2K2/8GX) £35.99
Total : £504.47 (includes shipping : £10.50).
People are using the Asus LX Z68 mobo as it's the cheapest Z68 at the mo. These mobos allow overclocking of K series CPUs, it's kinda pointless putting an i3 in them but as the other guys have said it's a good base for an i5 or ivybridge upgrade later. There are H series mobos much cheaper (£40ish) that don't allow overclocking but would help you save some cash to go elsewhere in the build.
I've used the GB mobo which has a PCI Express 3 lane (the 7850 supports this but you need an ivybridge CPU in the PC), has a 3 year warranty and there is also a nice thread on the forum to overclocking an i5K with that mobo.
The XFX PSUs are nice and have a 5 year warranty. My OCZ choice is cheaper still has plenty of "juice" and a 3 year warranty so not a bad trade off for price.
The case has USB3 ports and cable management to keep the cables behind the mobo and allow better airflow for cooling.
For £600ish you could swap out the i3 2120 for an i5 2500K and get a £20ish aftermarket heatsink in there too. You could then run the i5 CPU at over 4ghz rather than the stock 3.3ghz.
Having said all this come wednesday the offers change so i might use different branded RAM or mobo maybe even change the case as well. With the ivybridge processors due the end of the month you really should be waiting and saving.....let's see what offers OCuk put out with the ivybridge CPU launch
Any questions or problems you might have on build day, you know where to find us