Processor: http://www.ebuyer.com/242140-amd-athl...
Motherboard: http://www.ebuyer.com/407432-biostar-...
RAM: http://www.ebuyer.com/191047-crucial-...
Hard Drive: http://www.ebuyer.com/272944-seagate-...
Graphics card: http://www.ebuyer.com/344116-sapphire...
Disk drive: http://www.ebuyer.com/410561-liteon-i...
power supply: http://www.ebuyer.com/158479-cit-400w...
Case: http://www.i-store-online.com/product_info.php?currency=GBP&language=en&info=p55749_advance-hunter-x-pc-tower-case-in-red-with-white-led.html
Thats around £300 in total. (Not including the OS)