No "get-out" clauses of any kind for BT. Its in their moving home Ts & Cs that a new 12 month contract must be agreed.
Depending on the status of the line in your new property ie. is it still active or has it been disconnected or just stopped , you could get The Phone Co-op to restart it with a minimum term of 3 months rental and thereafter terminate with 1 months notice or use The Post Office which has no minimum term to re-install the line if its been disconnected.. As for broadband ISPs such as Newnet do monthly agreements.