| | when moving to fibre...
If it's FTTC your copper pair will be rerouted through the nearby
green cabinet to the DSLAM for the FTTC service.
So how will the phone still work?
Somebody with more patience than me has already answered that one for you.
If your existing router will workk with VDSL it might reboot itself
and carry on.
I've been told by "the system" - it won't work
How it knows that, I have no idea.
It's the safest option from their standpoint.
They did supply the old router, but they can't exclude the possibility
that I have stopped using it and bought my own, can they?
If you had bought your own you presumably would know what you had
bought, why, and whether it would support VDSL.
I assumed that they were fundamentally different, but you are saying not.
Just a bit different. Some do ADSL only, some might do VDSL only for
FTTC, some might do both ADSL and VDSL and configure themselves
- having a spare can't hurt.
It can hurt my wallet
Having insurance can hurt your wallet but in many cases it's a good
idea. Except for business interruption insurance when Covid-19 strikes,
when it seems to have been no better than a chocolate fireguard!