The landlord may, subject to the provisions of this section, serve on the tenant at any time a written notice requiring him—
if all relevant matters have been agreed or determined, to complete the transaction within a period stated in the notice, or
if any relevant matters are outstanding, to serve on the landlord within that period a written notice to that effect specifying the matters,
and informing the tenant of the effect of this section and of section 141(1), (2) and (4) landlord's second notice to complete).
The period stated in a notice under this section shall be such period (of at least 56 days) as may be reasonable in the circumstances.
A notice under this section shall not be served earlier than three months after—
the service of the landlord's notice under section 125 (notice of purchase price and other matters), or
where a notice has been served under section 146 (landlord's notice admitting or denying right to acquire on rent to mortgage terms), the service of that notice.
A notice under this section shall not be served if—
a requirement for the determination or re-determination of the value of the dwelling-house by the district valuer has not been complied with,
a review notice (within the meaning of section 128A) has been served in relation to such a determination or re-determination, section 128B applies and the district valuer has neither—
served a notice under section 128B(3) (refusal to make further determination), nor
served a notice under section 128B(7) (a determination effect notice),
no such review notice has been served but such a notice may still be served under section 128A,
proceedings for the determination of any other relevant matter have not been disposed of, or
any relevant matter stated to be outstanding in a written notice served on the landlord by the tenant has not been agreed in writing or determined.
In this section "relevant matters" means matters relating to the grant . . ..