CPU: AMD FX-6300 3.5GHz 6-Core Processor (£82.49 @ Ebuyer)
Motherboard: Asus M5A78L-M/USB3 Micro ATX AM3+ Motherboard (£49.49 @ Ebuyer)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory (£65.76 @ Scan.co.uk)
Storage: Western Digital Caviar Green 1TB 3.5" 5400RPM Internal Hard Drive (£37.00 @ Amazon UK)
Video Card: Asus Radeon HD 7850 1GB Video Card (£135.38 @ Dabs)
Wireless Network Adapter: TP-Link TL-WN751ND 802.11b/g/n PCI Wi-Fi Adapter (£9.00 @ Aria PC)
Case: Zalman Z5 ATX Mid Tower Case (£32.98 @ Ebuyer)
Power Supply: Corsair CX 500W 80+ Bronze Certified Semi-Modular ATX Power Supply (£46.59 @ Amazon UK)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) (£72.16 @ CCL Computers)
Monitor: Hannspree HE225DPB 21.5" Monitor (£89.94 @ CCL Computers)
Total: £620.79
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-12-26 16:08 GMT+0000)
http://uk.pcpartpicker.com/p/2qhFU
Slightly over budget but should definitely have some good performance. Should be able to play games such as BF4 on high possibly ultra settings.