I'm going for AMD myself (smaller budget) but I'll have a stab at this.
From the parts you list I assume you have case, OS etc.
CPU: Core i5 2500k - £165
Mobo: Perhaps someone else can help here
GPU: Radeon HD6850 - £110
Ram: G-Skill Ripjaws 8Gb - £40
PSU: OCZ Fatal1ty 550w - £50
Total £365 and should get very high
Hope that helps to get you started