18.—(1) Except in a case where an application has been referred to the Department under paragraph 17 and subject to paragraph 23, the enforcing authority shall give notice of—
(a)for Part A installations and for Part A mobile plant, its draft determination of an application for a permit, within the period of six months beginning with the day on which it received the duly made application;
(b)for Part B and Part C installations and Part B and Part C mobile plant, its determination of an application for a permit, within the period of six months beginning with the day on which it received the duly made application; and
(c)in any case, within such longer period as may be agreed with the applicant.
(2) For the purpose of calculating the periods mentioned in sub-paragraph (1) no account shall be taken of—
(a)any period beginning with the date on which notice is served on the applicant under paragraph 6 and ending on the date on which the applicant furnishes the information specified in the notice;
(b)any period allowed for making representations in relation to a notice given pursuant to paragraph 14 in so far as that period does not overlap with any other period allowed for making representations in accordance with paragraph 15;
(c)where a matter falls to be determined under regulation 34 or 35, any period beginning with the date on which the period of 28 days referred to in paragraph 7 ends and ending on the date on which the application is advertised in accordance with paragraph 30(a);
(d)where separate applications are made to operate different parts of one installation, any period beginning with the date on which notice is served on any of the applicants under paragraph 6 and ending on the date on which the applicant furnishes the information specified in the notice.