My enthusiasm sinks a bit when I read "BT Voyager" as I have not yet had the pleasure (if you could call it that) of setting up one of these, so I don't have enough knowledge about them. If it's one of the "big four" I know where I'm at.
1) You're not creating an ad-hoc network, so don't go too far down that road.
2) WEP is a basic form of encryption/password system, and you should a) not be using it at all yet and b) using WPA-PSK instead.
Tell me how far you have got with the router config page and we'll work from there.
(Meanwhile, if any experienced Voyager owners are reading this...)