I would recommend the i5 if you where gaming. That i5 CPU will last for 2-3 years on high+ details on games. It's easily overclocked (to some extent) so if you ever need more power, you can easily get it. When it comes to rendering and the likes, it is pretty fast, no doubt about it but it's noting special either.
The i7 would be a waste of money for games because games do not make efficent use of hyperthreading. You would only see a 3-5 FPS increase with the i7. But rendering is where this CPU comes in handy. It will perform better with that than the i5 but in my opinion I don't think its worth the extra £100.
As for the GPU I'm not really sure about it. You could play on BF3 maxed with a £130 ATI card. I would personally lock any extra money away for the future when better cards are cheaper.
So in summary: Get the i5 2500K. Easy to overclock if needed and can just about all games high/maxed for several more years to come. Also, the performence margin from the i7 is not that huge, in my opinon not worth a extra £100
Edit: Here are some handy benchmarks for the two CPUs:
AnandTech - Bench - CPU
I don't recommend going by the benchmarks alone though, it would be worth Googleing some reviews
Hope I helped