Paragraph 28 I1

substantial performance of a contract constitutes the effective date of that transaction by virtue of a relevant deeming provision,

the main subject-matter of the transaction consists of or includes an interest in a building, or a part of a building, that is to be constructed or adapted under the contract for use as a single dwelling, and

construction or adaptation of the building, or the part of a building, has not begun by the time the contract is substantially performed.