(1)If a dwelling-house ceases to be a qualifying dwelling-house otherwise than on a sale of the relevant interest in the dwelling-house, this Part has effect as if—
(a)the relevant interest in the dwelling-house had been sold at that time, and
(b)the net proceeds of the sale were equal to the market value of that interest at that time.
(2)For the purposes of this Part—
(a)a dwelling-house is not to be regarded as ceasing altogether to be used merely because it falls temporarily out of use, and
(b)if, immediately before any period of temporary disuse, a dwelling-house is a qualifying dwelling-house, it is to be regarded as continuing to be a qualifying dwelling-house during the period of temporary disuse.