they say the total is plus "buyer protection" and then plus 20% VAT.
It's so hard to help when all we have is "what people say". This may - and should - simply mean that 20% VAT is payable on eBay's buyer protection charge.
If we had the full facts we could at least have had a stab at suggesting whether you or the buyer had overlooked something, or whether eBay had made a mistake.
Without even knowing the agreed selling price or whether it was sold for delivery or collection it's impossible to work out what should have been payable by the buyer.
On the face of it, it certainly sounds like a mistake, but we are not eBay customer service. I suggest that one or both of you try to resolve this with eBay, then hopefully relist the item as a "buy now" sale at the price you agreed. Let the buyer know immediately you have listed it so that someone else doesn't get there first!
