UPDATE 2024! We now have a voice reinjection faceplate/kit available! https://www.run-it-direct.co.uk/adsl-vdsl-faceplates/voip-voice-injection-kit/
This scenario is becoming more common as the UK adopts a full fibre network. You get your nice new equipment and have it all fitted.....now that DECT phone you had plugged in upstairs no longer works!! What have they done?!
FTTH (Fibre To The Home) or FTTP (Fibre To The Premises) does not use any copper wiring. The voice side is now basically VoIP (Voice Over IP), or Digital Voice as BT are calling it.
If you had old extension wiring this is now no longer connected to anything. The fix is simple, VERY simple!
On the new equipment there will be a BT socket, most probably marked Tel 1 or ATA.
You need a cable of suitable length to go from this socket back to the BT socket on your old master socket.
We have suitable leads here : - https://www.run-it-direct.co.uk/bt-to-bt-patch-leads/
Before you plug the lead into the master socket you MUST first remove the front plate AND the back plate from the master socket. At the rear there will be two wires connected to A & B. These must be removed and left loose in the back box. Doing this isolates your extensions from the BT (old copper) network!
Your old extensions will now work just like they used to.
Note, if your faceplate looks like this : -
The socket for extension wiring is NOT a BT431A socket, you will require a specific cable (currently not available!).