4. The provisions of Part 2 (and of Part 5, so far as applying in relation to obligations under Part 2) do not apply to the showing of a product which is not in conformity with Part 2, at a trade fair, exhibition or demonstration, provided that a visible sign clearly indicates that—
(a)the product is not in conformity with Part 2; and
(b)the product is not available for sale until brought into conformity with Part 2.