Return of goods following cancellation (Regulation 17)
Who pays for returning the goods if the consumer cancels
an order?
3.55 If you want the consumer to return the goods and to pay for that
return, you must make it clear in the contract and as part of the
required written information – see paragraph 3.10. If the consumer
then fails to return the goods, or sends them at your expense, you
can charge them the direct cost to you of the return, even if you
have already refunded the consumer’s money. You are not allowed
to make any further charges, such as a restocking charge or an
administration charge.
3.56 If you did not include these details in the required written information
then you cannot charge anything.
So have a look at their order confirmation as to what they say. If they don't say anything then it is theirs to pick up