Ebuyer sells the Zoostorm 7873-1082 desktop PC for £270 (£250 after a £20 cashback direct from Zoostorm, one which you will have to claim before the end of August). You can possibly get another £75 cashback (which would bring the cost of the device to under £175) when you trade in an old computer. Ebuyer stresses that you will need to read the terms and conditions carefully prior to purchase.
The Zoostorm 7873-1082 is devoid of any operating system (we recommend Windows Home Server 2011 for that), monitor, keyboard or mouse. As for the components, the list includes an AMD A8-5500 APU, a quad-core model clocked at 3.2GHz with 4MB of cache and an AMD Radeon HD 7650D GPU that uses system memory.
There's also 8GB of RAM, a 2TB hard disk drive, a DVD writer, a Realtek GbE LAN and a 300w PSU. Connectivity and expansion capabilities include PS2, VGA, HDMI, six USB ports, three audio ones, PCI-e x16, PCI and PCI-e x1 slots. The case however is a microATX model which means that you won't be able to add more than a couple of hard disk drives.