(1) In this section -
"conversion expenditure" means, subject to subsection (2), expenditure incurred on -
(a) the conversion into a house of a building -
(i) the site of which is on a designated island, and
(ii) which has not been previously in use as a dwelling,
and
(b) the conversion into two or more houses of a building -
(i) the site of which is on a designated island, and
(ii) which, prior to the conversion, had not been in use as a dwelling or had been in use as a single dwelling,
and references in this section and section 70 to "conversion", "conversion into a house" and "expenditure incurred on conversion" shall be construed accordingly;
"qualifying lease", in relation to a house, means, subject to section 70(1), a lease of the house the duration of which is not less than 12 months and the consideration for the grant of which consists -
(a) solely of periodic payments all of which are, or fall to be treated as, amounts by way of rent for the purposes of Chapter VI of Part