Both you and john2007 are going down the path I suggested to wildthing that it is an LLU problem. However he has specifically denied this, saying it is the phone supply that is what cannot be done.
How that can be the case defeated me until I read this -
"the line in this property was connected to BT and that was in another persons name (the ex-wife's)".
If the existing service phone and broadband contract at his current address is in his ex-wife's name then he won't be able to move it. I don't see how he could cancel it either!
I'm quite sure that for whatever reason the situation is more complex than we have been told so far. As he will read this, I'm sure he will enlighten us as to whose name the contract is in. For the Home Phone to be in his name would be very odd if it wasn't his line to transfer to O2. Though maybe it is.
[puzzled]