12—Where the interest to be acquired is or includes a house in relation to which a grant has been made under Part XIII—
(a)observance with respect to the house of any of the conditions specified in section 246 (conditions to be observed with respect to a house in respect of which a grant has been made) shall cease to be required with effect from the time of disposal of the interest and paragraph 6 of Schedule 19 (requirements as to records when observance of conditions ceases to be required) shall apply as it applies in the case there mentioned; and
(b)the owner for the time being of the house shall not be liable to make in relation to the grant any payment under Schedule 19 (consequences of breach of conditions) unless the liability to do so arises from a demand made before the time of disposal of the interest.