Paragraph 7
The right to buy does not arise if the dwelling-house has features which are substantially different from those of ordinary dwelling-houses and are designed to make it suitable for occupation by physically disabled persons, and—
(a)
it is one of a group of dwelling-houses which it is the practice of the landlord to let for occupation by physically disabled persons, and
(b)
a social service or special facilities are provided in close proximity to the group of dwelling-houses wholly or partly for the purpose of assisting those persons.