Thanks for the helpful replies.
Waiting for, or getting through to a Virgin Media telephone number is like banging your head against the wall. I gave up on that a long time ago.
There seems to be no way to communicate with them by email and the only other option is to use 'snail mail'!
Consequently, I have just informed every contact who uses my VM email address to use my Gmail address in future. As for my bills, I'm sure VM will take the money anyway, as the money is all they seem to be interested in!
In fact, I have been considering moving to another supplier for some time. Unfortunately, all of the other ones available locally cannot deliver above 11Mb/sec. There is the possibility of Vodaphone Home Broadband using 5G, though.