A contract of supply of goods or services or a provision in or that relates to a contract of supply of goods or services is void if that contract or provision—
(a) purports to have the effect of excluding, restricting or modifying the provisions of section 27 or 28; or
(b) purports to have the effect of precluding a right of action or a defence based on or arising out of a representation or a warranty referred to in section 27(1) or (2).