What you want won’t be easy to accomplish , it may not even be possible , and if orders have already been issued it may already be to late retrieve now anyway.
Number portability has rules , what you want to do doesn’t fit in with these rules.
If the idea is to avoid early termination charges, then if both addresses are within a minimum term that’s not possible, plus both addresses will have to be connected to the same exchange.
If the TT number is required but with BT as the provider , the TT account holder would simply have to migrate to BT, using number portability you simply cancel your service at your address, the account would remain in that household name.
If you wanted to take your account/service with you to that address , you could take over the TT service but that wouldn’t keep the TT number, the takeover just cancels the TT service
You arranging for BT to take over the TT service in your name but keeping the TT number from the other householder name is ( IMHO ) not possible
If the reason you want to do this is to avoid ETC , or wanting BT for some other reason, you would have to get a second line installed with BT ( your account ) alongside the existing TT service
