This cabinet is temporarily unavailable for fibre orders due to engineering works." First question is anyone have any idea what this is likely to mean?
Possibly full, requiring more capacity to be added.
Secondly, no ISP other than BT will offer him FTTC speeds, & therefore prices. BT describe these as Full Fibre so I'm guessing it's the equivalent FTTC packages being offered over FTTP? This ties in with different guaranteed speeds being offered whereas an FTTC product would have a fixed max speed across the packages.
Does the Wholesale checker show WBC FTTP as available to him?
Assuming this is correct it raises an issue with his analogue phone line. He has several extensions with analogue handsets & an alarm system with an analogue dialler he would like to retain. It's very unclear from my reading elsewhere whether this is likely to still be possible. Will he be forced to go to VOIP?
If it's FTTP then the BT system dictates if VOIP will be used for calls or if the copper line will be used.
If the BT order mentions Digital Voice, then it's VOIP only.
If the system says VOIP is available then that will be used.
It cannot be changed.
You really need to tell your friend to sort out their alarm.
PSTN will be switched off by 2025, earlier in some areas.
Some ISP's have already completely ditched PSTN for all new FTTC customers.
They are just delaying the inevitable.
Lastly with them both working from home in critical roles, it's essential the service is stable. Would it be possible to retain the Zen ADSL service in parallel with a new BT FTTP service for a month or two to confirm stability of the new connection?
Yes.