@andyt1970
Like most others on here I am not a staff member.
To get definitive answers you need to SPEAK to COTs.
It costs PN money to transfer your account which they recover over the life of a contract by getting a customer to agree a new one. The terms you are offered could be different at this time from what's on offer now but you just have to accept this if moving.
Ensure the owner of the property gives plenty of notice for the cancellation. You don't want to get caught out by the 10 day OFCOM mandated cooling off period between cancellation of a line and it being taken over (by you).
Brian