28. (1) A purchaser may, on the fifth or any subsequent anniversary of the vesting date during the charged period and with the consent of the housing authority—

(a) pay to the housing authority, on the anniversary date or within such period as the housing authority may specify, the value of the outstanding charged share in the house on any such anniversary date (including an incremental release suspended by the authority under section 27(1)), which value is calculated by applying that share to the relevant market value of the house on that day,

(b) subject to subsection (2), pay to the housing authority an amount, being the value on any such anniversary date of one or more than one incremental release (other than an incremental release suspended by the authority under section 27(1)) in respect of the charged share of the housing authority in the house, and where the value of one incremental release is calculated as 2 per cent of the relevant market value of the house on the anniversary date concerned.

(2) A payment by a purchaser under subsection (1) (b) shall relate to a number of incremental releases that is equal to or a multiple of one.

(3) Where a purchaser makes a payment to the housing authority under subsection (1) (b), then—

(a) for the purpose of calculating the outstanding charged share in the house, an incremental release paid under this section shall be treated as if it has been applied to the charged share on the date concerned, and

(b) the charged period shall be reduced by the number of years equivalent to the number of incremental releases to which the payment relates.

(4) For the purposes of this section, the relevant market value of a house shall be determined by the housing authority or, where the vendor does not agree with the relevant market value so determined, by an independent valuer nominated by the vendor from a panel of suitably qualified persons, established by the housing authority, who are of a class or description prescribed under section 30.