A further development to the questions below. As a very helpful contributor suggested, I called Virgin to arrange for an engineer to come and reroute the cable tv and hub to enable the phone line to connect to the hub. They booked an engineer for 29th November and informed me that the fibre switchover was scheduled for the same day. So there was no immediate urgency.
I came back on 4th November to find that the phone line was dead. I knew what had happened, but phoned Virgin to ask why it was not working and they said the switchover had been done. When I told them I had been given assurances nothing would happen until 29th, there was no apology, no acknowledgment of the problems this has caused, just a promise that I would get a call from the tech team the following day between 8am and 12pm. This call never happened and I phoned again. Again, no apology and no acknowledgement, and I was told I had no need to worry because I would definitely get a call that day.
It is now the following day and there has been no call. I have had enough and have readied an order for Sky. We are out of contract with Virgin, so it will not cost anything further with them. I didn’t mention before that it is not my house, it is my elderly mother’s and the phone is connected to a panic alarm which no longer works either. I told Virgin all this but they don’t seem to care.
If Virgin would just sort out the mess they have made, I would probably stay with them, but it seems inevitable that nothing will happen until the date that suits them and they don’t care about leaving an older person without a phone or panic alarm until then.