Actually H, you can, but you need to flash your BT Fibre Modem with a different Firmware version.

Go read about it over @ Kitz

http://www.kitz.co.uk/routers/hg612unlock.htm

This link will take you to the Unlocked firmware page.

https://docs.google.com/file/d/0B6wW...U3c/edit?pli=1

Hold mouse over Unlocked002 file & click the arrow over to the right of the name string.

Enjoy.