50.—(1) A judge of the court or the registrar may extend the period for service of a respondent's notice under rule 49(4) (even after it has expired).
(2) If a judge of the court or the registrar exercises, or refuses to exercise, the power under paragraph (1), the registrar must, within seven days after the date of the exercise or refusal, serve notice of his decision on the appellant and the respondent.
(3) If the registrar refuses to exercise the power under paragraph (1), the respondent shall be entitled to have the application for the exercise of the power determined by a judge of the court.
(4) If a judge of the court refuses to exercise the power under paragraph (1), the appellant or respondent shall be entitled to have the application for the exercise of the power determined by the court as duly constituted for the purpose in accordance with section 5.