In this Part "suitable alternative accommodation", in relation to the occupier of a dwelling, means a dwelling as to which the following conditions are satisfied—
he and his family can live in it without causing it to be overcrowded;
it is certified by the local housing authority to be suitable to his needs and those of his family as respects security of tenure, proximity to place of work and otherwise, and to be suitable in relation to his means;
where the dwelling belongs to the local housing authority, it is certified by them to be suitable to his needs and those of his family as respects accommodation.
For the purpose of subsection (1)(c) a dwelling containing two bedrooms shall be treated as providing accommodation for four persons, a dwelling containing three bedrooms shall be treated as providing accommodation for five persons and a dwelling containing four bedrooms shall be treated as providing accommodation for seven persons.