Heres your case Casecom 6788 all black interior £24.99
Heres the RAM Corsair DDR3, 1600MHz 4G 2x240DIMM, Unbuffered, 9-9-9-24, XMS3 4GB £88
Heres the Mobo
http://www.gigabyte.com.tw/Products/Motherboard/Products_Spec.aspx?ProductID=3168 £73
I havent included the GFX card but i assume the only DX11 card on the table wud be 5770 which will set you back around £125, however, if your screen is bigger than 19` i wud opt for a 4890 at around £140 or save up for a DX11 5850 which are around £200.
Ive tried to cost this as low as pos but you have to decide weather you want to spend the extra on i5 which is well worth it imo otherwise i will help you with a Core2 Duo or AMD set up
Heres the CPU Intel core i5 £145
Heres ya Hard Drive Hard+Drives/Serial+ATA/Hitachi+3.5%22+Deskstar+320GB+16MB+SATA+7200rpm+HDD £32
OR Hard+Drives/Serial+ATA/500GB+Maxtor+DiamondMax+23+SATA+3Gb%2Fs+Hard+Drive
OR Hard+Drives/Serial+ATA/1TB+Samsung+Spinpoint+F3+SATA2+7200RPM+32MB+cache+HD103SJ
Heres your PSU Be Quiet 600W Straight Power E7 PSU £69.99 & free shipping
Heres your DVD Burner LG Super Multi £16
This will total up over your budget but it is worth considering, actually comes to £449 minus the graphics card
Sorry bout that the links are awry, i`ll try to fix it No complete waste of time, i cant understand why the links work when you peview them but when you post it turns into gobbldy gook, geez, if you want to check them out yourself you can still see the part numbers and the prices can be got by visiting @ria dot co dot uk and also £buyer dot com it just turns out that the prices are cheaper than OCUK. So your not allowed to mention competitors OK i`ll know next time