If, under a tenancy, a dwelling-house is let together with other land, then, for the purposes of this Part of this Act,—
if and so long as the main purpose of the letting is the provision of a home for the tenant or, where there are joint tenants, at least one of them, the other land shall be treated as part of the dwelling-house; and
if and so long as the main purpose of the letting is not as mentioned in paragraph (a) above, the tenancy shall be treated as not being one under which a dwelling-house is let as a separate dwelling.
Nothing in subsection (1) above affects any question whether a tenancy is precluded from being an assured tenancy by virtue of any provision of Schedule 1 to this Act.