if your existing BB provider is sky, then my one did work
* I had sky adsl2+
* ordered Sky fibre
* received new router
* Installed new router, plugged into the master socket, to make sky adsl2+ work
* Fibre installed, with separate BT modem unit (engineer install)
* Connected new sky router WAN cable into router to make FTTC work.
I understand the new sky routers for fttc plug directly into the telephone socket and work for adsl/fttc no matter what the signal, so should just work.