Have just checked the relevent section of Planning (Listed Buildings and Conservation Areas) Act 1990 which says:-
Execution of works required by listed building enforcement notice. E+W.(1)If any of the steps specified in the listed building enforcement notice have not been taken within the period for compliance with the notice], the authority may—.
(a)enter the land and take those steps, and.
(b)recover from the person who is then the owner of the land any expenses reasonably incurred by them in doing so..