Even cheaper purchased from New Zealand on Trademe (our 'Ebay'). They are apparently selling for NZ$150 (80 GBP) new in box. They are standard retail NZ$299, on special occasionally for $NZ199, or being given away by Telecom as a bribe to keep broadband customers.
The 1GB version is likely to be released once the stocks of 320GB units are cleared, and no doubt will be much more expensive.
Shipping can be accurately calculated here http://www.nzpost.co.nz/sending-internationally/parcels
I may have time to do this for you, esp if you purchase the TiVos online and have them shipped to me (Bond & Bond or Noel Leeming had free shipping).