Four years ago I moved into a house where the line and broadband was all TalkTalk. They said I'd need to get the previous occupant to terminate service before they could provide me service at the address.
I'd have to pay £125 to BT for a new line (TalkTalk didn't provision lines, they just took-over existing BT lines), £90 to BT for an early termination so I could pay £30 to TalkTalk to migrate. £245 and a month of faff to basically change the name on the contract!
BT wouldn't offer me "return to donor" because I was a new customer.
Every time I've moved before the line had already been with BT and there'd been no charge to re-activate it. All this LLU nonsense cost me £155.
BT has their faults, but at least they don't pick-and-choose which bits of service they'll provide.