You can get the 4770 for around £250 and the 4770k for around £270. Coupled with the Asus z87 pro motherboard at £150, you can't go far wrong (if you can afford the extra £20, the letter K on the end of the processor is totally worth it imo
)
What's the system for? If you're gonna be gaming, consider getting the i5 4670K for around £180 and putting the spare £70 towards a better GPU, or even a 120hz monitor?
Edit: all prices taken from dabs.com