Part II of Schedule 18 to this Act shall have effect where a premium was lawfully required and paid on the grant, renewal or continuance of a regulated tenancy—
(a)which was granted before 8th March 1973, and
(b)which would not have been a regulated tenancy, but for section 14(1) of the [1973 c. 9.] Counter-Inflation Act 1973 (which brought certain tenancies of dwelling-houses with high rateable values within the protection of the [1968 c. 23.] Rent Act 1968).