This Western Digital 160GB Passport V2 External USB 2.0 2.5" Hard Drive, is USB powered and just £70.48 including delivery @ Amazon ( its so small!).
Thanks to rayman for the pointer !!
Features: WD Passport WDXMS1600 - hard drive - 160 GB - Hi-Speed USB * Type: Hard drive - external * Form Factor: 2.5" * Dimensions (WxDxH): 8 cm x 13 cm x 1.5 cm * Weight: 105 g * Capacity: 160 GB * Interface Type: Hi-Speed USB * Connector: Mini-USB * Data Transfer Rate: 480 Mbps * Average Seek Time: 12 ms * Spindle Speed: 5400 rpm * Buffer Size: 2 MB * OS Required: Microsoft Windows 2000, Microsoft Windows XP, Apple MacOS X 10.1.5 or later * Power Source: USB bus