This should be perfect for you ! The MSI Geforce GTX 770 lightning is the best of its category, and you would have a hard time fitting it into a different build.
PCPartPicker part list:
http://uk.pcpartpicker.com/p/1shMt
Price breakdown by merchant: http://uk.pcpartpicker.com/p/1shMt/by_merchant/
Benchmarks: http://uk.pcpartpicker.com/p/1shMt/benchmarks/
CPU: AMD FX-8320 3.5GHz 8-Core Processor (£107.99 @ Aria PC)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler (£22.85 @ CCL Computers)
Motherboard: Gigabyte GA-78LMT-USB3 Micro ATX AM3+ Motherboard (£38.69 @ Ebuyer)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory (£60.86 @ Dabs)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£46.80 @ Aria PC)
Video Card: MSI GeForce GTX 770 2GB Video Card (£336.99 @ Ebuyer)
Case: Cooler Master Force 500 ATX Mid Tower Case (£32.87 @ Scan.co.uk)
Power Supply: Corsair CX 600W 80 PLUS Bronze Certified ATX12V Power Supply (£58.08 @ Dabs)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer (£12.94 @ Amazon UK)
Operating System: Microsoft Windows 8 (OEM) (64-bit) (£68.39 @ Aria PC)
Total: £786.46
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-15 18:44 BST+0100)