this is the cheapest i could make it.
PCPartPicker part list:
http://pcpartpicker.com/p/zN9w
Price breakdown by merchant: http://pcpartpicker.com/p/zN9w/by_merchant/
Benchmarks: http://pcpartpicker.com/p/zN9w/benchmarks/
CPU: AMD FX-4300 3.8GHz Quad-Core Processor (£88.20 @ Aria PC)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler (£25.45 @ Scan.co.uk)
Motherboard: Gigabyte GA-970A-DS3 ATX AM3+ Motherboard (£51.78 @ Amazon UK)
Memory: Crucial 8GB (2 x 4GB) DDR3-1600 Memory (£32.36 @ Dabs)
Storage: Seagate Barracuda 500GB 3.5" 7200RPM Internal Hard Drive (£37.19 @ Aria PC)
Video Card: XFX Radeon HD 7850 1GB Video Card (£126.94 @ Scan.co.uk)
Case: Cooler Master RC-361-KKN1 (Black) ATX Mid Tower Case (£28.78 @ Scan.co.uk)
Power Supply: XFX ProSeries 450W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply (£36.98 @ Novatech)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer (£12.98 @ Scan.co.uk)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) (£67.96 @ CCL Computers)
Total: £508.62
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-01-27 02:54 GMT+0000)
508$ pounds, nice build there dj but its 72$ over budget.