Thanks AphJN.
MikeB4ugo - I've split this into a new thread for you.
This isn't my area of expertise but BT have told me that there isn't a password used for the standard BT Broadband connection. Have you tried it with
firstname.surname@btbroadband.com and no password?
The Netgear router will require a WAN connection as it is going outside of any internal Local Area Network (LAN) inside your building. However, I believe that routers are usually internally programmed to make their own connection to the outside world as soon as they are plugged in. It sounds like Netgear advise to disable the BT connection so that it doesn't try to make a second connection and cause a conflict.
Hope that helps in some way.