payment of duties

My partners Ebay site had sold a large tablecloth to united kingdom,

The buyer writes back to say that the parcel had been delivered but is in customs and they want 18 pounds before release

Buyer complains that cant afford the duty and will let the item come back to Australia 

then expects a full refund as the buyer said i should have been aware for the duty charge and should have let them know

My reply.....sorry that YOUR parcel is in customs but its your responsability to pay any taxes or duties that arise in YOUR country

Buyer is not happy and will take it further

any comments welcome