Tesco direct are doing an external 500gb usb2 hard drive for 122.97, it can also be connected via an included E-SATA PCI card for a speed increase:

iQon External 500GB Hard Disk

  • Hard Drive Size: 3.5"
  • Interface: SATA
  • Rotational Speed 7200rpm
  • Features 500GB E-SATA External HDD, USB 2.0 connection, E-SATA PCI Upgrade Kit, Plug & Play, Hot Swappable
  • Accessories Included E-SATA cable, E-SATA PCI Upgrade Kit, USB Cable, Power Cable


Cheers

Ed.