(1) In this section -
"qualifying lease", in relation to a house, means, subject to section 350(2), a lease of the house the consideration for the grant of which consists -
(a) solely of periodic payments all of which are or are to be treated as rent for the purposes of Chapter 8 of Part 4, or
(b) of payments of the kind mentioned in paragraph (a), together with a payment by means of a premium which does not exceed 10 per cent of the relevant cost of the house;
"qualifying premises" means, subject to subsections (3), (4)(a), (4)(c) and (5) of section 350, a house -
(a) the site of which is wholly within a designated area,
(b) which is used solely as a dwelling,
(c) the total floor area of which -
(i) is not less than 30 square metres and not more than -
(I) 125 square metres, or
(II) as respects expenditure incurred before the 12th day of April, 1995, 90 square metres,
in the case where the house is a separate self-contained flat or maisonette in a building of 2 or more storeys, o