3Section 48(1) of this Act shall not apply to any improvement completed before the conversion, but if the rent recoverable for the last rental period beginning before the conversion was less than it would have been if all notices of increase authorised by virtue of section 32 of this Act (or, as the case may be, section 56 of the [1968 c. 23.] Rent Act 1968) had been served, the rent recoverable under section 45(1) of this Act, as modified by paragraph 2 above, shall be increased by the amount of that difference.