When we do e-bay auction for stuff from the shop we alway put in big letters "PLEASE ADD VAT TO THE FINAL PRICE". We try and make it as clear as possible so there is no misunderstanding. You also get a VAT invoice with the item.
If he has not stated it clearly in the description then don't pay it. If he is a trader then he won't want the negetive feadback. If you deside to pay it, ask for a proper VAT invoice.
John