Any agreement for the purposes of section 14 above shall be made with respect to such period of 12 months as may be specified in that agreement and, without prejudice to the making of a further agreement, shall cease to be in force at the expiry of that period.

An agreement for the purposes of section 14 may be revoked at any time by 3 months’ notice in writing, but shall not cease to be in force until the expiry of that notice.