Consider this build:
PCPartPicker part list:
http://uk.pcpartpicker.com/p/dTB6qs
Price breakdown by merchant: http://uk.pcpartpicker.com/p/dTB6qs/by_merchant/
CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor (£176.99 @ Aria PC)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler (£24.25 @ Scan.co.uk)
Motherboard: MSI Z97-Gaming 3 ATX LGA1150 Motherboard (£93.99 @ Ebuyer)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory (£55.34 @ Scan.co.uk)
Storage: Western Digital BLACK SERIES 1TB 3.5" 7200RPM Internal Hard Drive (£55.99 @ Amazon UK)
Video Card: MSI GeForce GTX 770 2GB TWIN FROZR Video Card (£228.95 @ Ebuyer)
Case: Corsair 200R ATX Mid Tower Case (£44.99 @ Amazon UK)
Power Supply: XFX 650W 80+ Bronze Certified Semi-Modular ATX Power Supply (£60.06 @ CCL Computers)
Operating System: Microsoft Windows 7 Professional SP1 (OEM) (64-bit) (£44.99 @ Amazon UK)
Total: £785.55
Haswell refresh CPU and it's overclockable.