Do you happen to know if Virgin do BT number porting ? I get the feeling
that they don't, as all of the people I know who have a Virgin phone, seem
to have a completely different number from the series of BT numbers which
serve my village.


Yes, you can transfer your BT number to Virgin, just tell Virgin that you
want to do that and they will do all the leg work.
One word of warning though, DON'T cancel yout BT account before arranging
the new account with Virgin.
If you do, you will loose your BT number.
Just contact Virgin and they will transfer the number for you AND they will
cancel your BT account at the same time.
I'm going through exactly that situation right now, and we've been with BT
for more than 45 years.

Wavey Dave