24Where the compulsory purchase order is confirmed by the Secretary of State, the control order ceases to have effect—
(a)if the local housing authority enter into a contract to purchase the house, on the date when the contract is made;
(b)if the local housing authority, in pursuance of a notice served under section 11 of the [1965 c. 56.] Compulsory Purchase Act 1965, enter and take possession of the house or serve a notice under section 583 of this Act (power to take possession without displacing tenant), on the date when the notice under section 11 is served.