If no joy it's possible to use your exiting wiring by splitting the extensions away from the incoming BT pair & patching that into the SH2. Easier still if you were also moved to full fibre.
Thank you all for your help. My partner is getting fed up with the constant ringing of phones 😂.
Have found our other phone, the BT Decor 2200 does give caller display through the plug adaptors, so at least we can now see who is calling. Have tried turning off the answerphone on the BT Paragon but this didn't help. Will update if any further progress.