13Where, in respect of Use before the appointed day of a registered design by virtue of paragraph 1 of Schedule 1 to the [1949 c. 88.] Registered Designs Act 1949, a payment has fallen to be, but has not been, made by the Postmaster General or would, if this Act had not passed, have fallen to be made by him, that payment shall be made instead by the Post Office; and, if the amount of the payment has not been agreed or determined as mentioned in sub-paragraph (3) of the said paragraph 1 before that day, it shall, in default of agreement between the Post Office and the person to whom the payment is due, be determined in like manner as it would have been determined had this Act not passed.