When buying from abroad, ebay. collects VAT for items up to £135, above that and it is import duty, which is collected on delivery plus a  collection charge.

Royal Mail for example require payment before delivery, some  couriers collect at delivery, others deliver then send an invoice for duty and fee.

As item was over £135 you did not pay duty on purchase. As said refusing to pay invalidates the money back guarantee, so can prove expensive, no item, no money.