I would definitely cancel this order, and not organise any courier on their behalf.
The courier may well come without that vital 6 digit QR code for you, and this is the only proof the item was collected. You would be responsible if the payment is coming directly from you, to pack the item safely too. So cost of packaging enters in the equation.
Cancel the order, citing Problem with Buyer's Address. This fully refund the buyer, and your seller performance is not affected.
Block them too from returning :
https://www.ebay.co.uk/bmgt/BuyerBlock?
@angeo261