18. Except in an emergency, in any case where it is proposed to enter any premises used for residential purposes, or to take heavy equipment on to any premises which are to be entered, any entry by virtue of this paragraph shall only be effected–
(a)after the expiration of at least seven days' notice of the proposed entry given to a person who appears to the authorised person in question to be in occupation of the premises in question; and
(b)either–
(i)with the consent of a person who is in occupation of those premises; or
(ii)under the authority of a warrant by virtue of Part 3 to this Schedule.