(1)If, in the case of a variation of the terms of a regulated tenancy, there is a failure to observe any of the requirements of section 51, 52(6) or 53 of this Act, any excess of the rent payable under the terms as varied over the terms without the variation shall be irrecoverable from the tenant.
(2)If, in the case of the grant of a tenancy, there is a failure to observe any of those requirements, any excess of the rent payable under the tenancy so granted (for any contractual or any statutory period of the tenancy) over the previous limit shall be irrecoverable from the tenant.
(3)In subsection (2) above the " previous limit" shall be taken to be the amount which (taking account of any previous operation of this section or of section 46 of the [1972 c. 47.] Housing Finance Act 1972, which is superseded by this section) was recoverable by way of rent for the last rental period of the previous tenancy of the dwelling-house, or which would have been so recoverable if all notices of increase authorised by this Act, the [1968 c. 23.] Rent Act 1968 and section 37(3) of the Act of 1972 had been served.
(4)A default which consists only in delay in complying with the requirements of paragraph (a) of section 52(6) of this Act shall only affect rent for any rental period beginning before the expiry of a period of 28 days beginning with the date when those requirements are complied with.
(5)A default in complying with paragraph (b) of section 52(6) of this Act shall not apply to rent for any rental period beginning after the default is made good.