If, at any time after a notice has been served under section 11A, 12A, 12B or 12C, the premises affected by the original disposal cease to be premises to which this Part applies, the purchaser may serve a notice on the qualifying tenants of the constituent flats stating—
A landlord who has not served such a notice on all of the qualifying tenants of the constituent flats shall nevertheless be treated as having duly served a notice under subsection (1)—
Where a period of three months beginning with the date of service of a notice under section 12A, 12B or 12C on the purchaser has expired—
the purchaser may serve on the nominated person a notice stating that the notice, and anything done in pursuance of it, is to be treated as not having been served or done.
Where any such application as is mentioned in subsection (3)(b) was made within the period of three months referred to in that subsection, but—
the purchaser may serve on the nominated person a notice stating that any notice served on him under section 12A, 12B or 12C, and anything done in pursuance of any such notice, is to be treated as not having been served or done.
Where the purchaser serves a notice in accordance with subsection (1), (3) or (4), this Part shall cease to have effect in relation to him in connection with the original disposal.
Where a purchaser is entitled to serve a notice under subsection (1) but does not do so, this Part shall continue to have effect in relation to him in connection with the original disposal as if the premises in question were still premises to which this Part applies.
References in this section to the purchaser include a subsequent purchaser to whom sections 12A to 14 apply by virtue of section 16(4) or (5).