New hardware list based on the 1.5u 19" rack mount case ...
Motherboard: Gigabyte GA-H77N-WIFI @ £85.97
CPU: Intel Core i3 3225 Dual Core CPU (Socket 1155, 3.30GHz, 3MB Cache, Ivy Bridge, 55W) @ £107.97
RAM: Corsair CMZ8GX3M2A1600C9 Vengeance 8GB (2x4GB) DDR3 1600 Mhz CL9 XMP Performance Desktop Memory Kit Black @ £58.97
CPU Cooler: Thermaltake Slim X3 CPU Cooler with 80 x 15mm Fan for LGA775 and LGA1156 @ £16.78
GPU: TBC @ £120.00 (budget)
Case: 1.5u Rack Mount, Model #: IPC-1.5U1525, Dimension (DxWxH): 250mm x 482mm x 68mm, Drive Bays: 1x (internal 3.5" bay), +2x (internal 2.5" bay) @ £58.80
http://www.xcase.co.uk/product-p/case-itx-03.htm
Total: £442.96 (28/7/13 - Amazon UK, X-case)
28/7/13 - Mac Mini, i5, 4Gb RAM, 500Gb HDD, Intel HD Graphics 4000, Thunderbolt, USB 3 @ £499.00