Not as far as I know. From
ebay's point of view you haven't performed as a seller.
Unfortunately the problem Ben (or anyone in that position) has is that proof of posting isn't proof of delivery. For valuable goods the only option is tracked and signed for delivery either through Royal Mail or one of the couriers. With cheaper items I accept the occasional "loss".
Bottom line is that PayPal are only interested in an online tracking number. People have been stung even where an item has been collected in person and the buyer has signed a receipt note - PP aren't interested.
Compensation from RM may require the buyer to confirm they haven't received the goods. So a dishonest buyer may not cooperate with this stage. You may be able to jolt the buyer into action by taking them to the small claims court or by involving the police. But it will still come back to the problem that you can't prove receipt (only dispatch). If you haven't already done it have a look in the ebay community forums. They are some very wise folk there (even if their advice is occasionally a bit sharp).