I don't know about availability in the UK, but the NZXT Phantom case looks really nice and has good cooling, if you're going for aesthetics. Also, good job on the MSI GPU. It seems like you're going for quietness/silence, though... 'cause of the CPU cooler. If you are, get a Fractal R3 case... it'll be quieter. If not, then try getting a Hyper 212 Evo as the CPU cooler... although again, I don't know about your retailers.
1 x8 gig of RAM will run in single channel and kill about 6-8 % of the computers performance .
Instead use 2 x4 gig of RAM , and be smart and use 1600 Mhz running at 1.5 volts or less . The mushkins timings are AWFUL . LOWER IS BETTER
bowman, I recommend an i5-2400 if you're not overclocking. It's the i5-2500k without the "K", and is better price/performance for a non-overclockable CPU. For Intel, anything with a "k" is overclockable. I really recommend the i5-2400, though.