Any provision in any agreement -
(a) whereby an owner or any person acting on his behalf is authorised to enter upon any premises for the purpose of taking possession of goods which have been let under a hire-purchase agreement, or is relieved from liability for any such entry, or
(b) whereby the right conferred on a hirer by this Act to determine the hire-purchase agreement is excluded or restricted, or whereby any liability in addition to the liability imposed by this Act is imposed on a hirer by reason of the termination of the hire-purchase agreement by him under this Act, or
(c) whereby a hirer, after the determination of the hire-purchase agreement or the bailment in any manner whatsoever, is subject to a liability which exceeds the liability to which he would have been subject if the agreement had been determined by him under this Act, or
(d) whereby any person acting on behalf of an owner or seller in connection with the formation or conclusion of a hire-purchase or credit