15.—(1) Where following the making of a proposal all the persons mentioned in paragraph (2) agree on an alteration of the list in accordance with this Part in terms other than those contained in the proposal, and that agreement is signified in writing—
(a)subject to paragraph (4), the valuation officer shall not later than the expiry of six weeks beginning on the day on which the agreement was made alter the list to give effect to the agreement; and
(b)the proposal shall be treated as having been withdrawn.
(2) The persons referred to in paragraph (1) are—
(a)the valuation officer;
(b)the person who made the proposal;
(c)subject to paragraph (3), the occupier (at the date of the proposal) of any hereditament to which it relates;
(d)the occupier (at the date of the agreement) of any hereditament to which it relates;
(e)any other person who—
(i)is an interested person who would have been competent to make the proposal, and
(ii)has within three months beginning on the day on which the proposal was served on the valuation officer served notice on him to the effect that he wishes to be party to proceedings in respect of the proposal; and
(f)the charging authority, where that authority would at the date of the proposal have been competent to make the proposal in question.
(3) Where—
(a)any occupier of the hereditament at the date of the proposal is, at the date on which all the other persons mentioned in paragraph (2) have agreed as mentioned in paragraph (1), no longer in occupation of any part of it, and
(b)the valuation officer has taken all reasonable steps to ascertain the whereabouts of any such occupier, but they have not been ascertained,
the agreement of that person under the foregoing provisions of this regulation shall not be required.
(4) Where the period of six weeks mentioned in paragraph (1 l(a) would expire before the period of three months mentioned in paragraph (2)(e) the alteration required by paragraph (l)(a) shall, where no notice is served as mentioned in paragraph (2)(e), be made as soon as practicable after the expiry of that period of three months.