Thanky you very much for this informative and usefull posting.
Using the details haere I am now happilly using sipgate with my (firmware downgraded) home hub.

1 note to add. I found that as well as adding "add name=BBT_servers type=ip addr=217.10.79.23" I also had to remove all existing lines startig "add name=BBT_servers".

Also found that for sipgate it didnt like the full sip uri in the gui setup, and would only work if I put my username in there.

one last thing.
Ive been trying to set it up to use the prefix 9, to force it to use the landline for a call, with no joy.

the line im using is "dialplan add prefix=9 defaultport=FXO fallbackport=VoIP priority=Low fallback=enabled minimumdigits=1 maximumdigits=1 posofmodify=1 remnumdigits=1 insert="" rescan=no data=no action=ROUTE_excl_eon
"

If anyone has any thoughts on where this is going wrong it would be greatly appreciated. (atm whatever number i dial after 9 takes me to a generic bt voicemessage telling me how to get to voicemail services)