9(1)The right to buy does not arise if—
(a)the dwelling-house is one of a group of dwelling-houses which it is the practice of the landlord to let for occupation by persons who are suffering or have suffered from a mental disorder, and
(b)a social service or special facilities are provided wholly or partly for the purpose of assisting those persons.
(2)In sub-paragraph (1)(a) “mental disorder” has the same meaning as in the [1983 c. 20.] Mental Health Act 1983