(4)Nothing in this section shall—(a)affect a condition in a contract by which a person is prohibited from selling goods other than those of a particular person;(b)validate a contract which, but for this section, would be invalid;(c)affect a condition in a contract for the lease of, or licence to use a patented article, by which the lessor or licensor reserves to himself or his nominee the right to supply such new parts of the patented article as may be required or to put or keep it in repair.
