18.—(1) This regulation applies on the cancellation of a contract under regulation 10 where the supplier agreed to take goods in part-exchange (the “part-exchange goods”) and those goods have been delivered to him.
(2) Unless, before the end of the period of 10 days beginning with the date of cancellation, the part-exchange goods are returned to the consumer in a condition substantially as good as when they were delivered to the supplier, the consumer shall be entitled to recover from the supplier a sum equal to the part-exchange allowance.
(3) In this regulation the part-exchange allowance means the sum agreed as such in the cancelled contract, or if no such sum was agreed, such sum as it would have been reasonable to allow in respect of the part-exchange goods if no notice of cancellation had been served.
(4) Where the consumer recovers from the supplier a sum equal to the part-exchange allowance, the title of the consumer to the part-exchange goods shall vest in the supplier (if it has not already done so) on recovery of that sum.