It will be something similar to here I expect.
http://screenshots.portforward.com/BT/BT2700HGV/LAN_-_Private_Network.htm
Settings>LAN>Private Network
Thanks, that's what I thought Steve, but having had a raft of problems trying to reset it and then unlock it I didn't want to end up bricking the thing, so thought I'd ask.
Yesterday iDNet reset my login (authentication) password. I'm sure there's a way of doing it easily using an unlocked 2-Wire but I couldn't find it, so in the end I temporarily reverted to the old Zyxel. This morning I did a full reset/unlock on the 2700 which is now back up and running.
I have to say I do like the 2-Wire routers. Frankly I doubt I would have heard of them were it not for 'Netters'. I have a couple of spares - both v6 unfortunately - but at £10 each (inc postage) they have to be a bargain, particularly on my line, which has a high attenuation.