Change from Sky LLU

This is a slight twist on a subject that seems to keep coming up. I am currently with Sky on a LLU exchange. My question concerns the line to my house. If I move and the new owner of this house doesn't want Sky do they (or me) have to pay to get the line back to BT, (or whoever) before they can get phone/broadband here?

The line reverts to stopped state when you move out, and the activation fees to get the line in the new persons name apply.
They don't have to worry about extra costs to get it back to BT or an equivalent

The important bit is that you time the shutting down of your phone and broadband, so it finishes on the day you move out