I had problems with a seller that had not sent me a radio that I had paid him £200 for. We had done the deal outside of ebay, and paid as a paypal gift, so I had no come back with them.
I messaged everyone on his ebay feed back that he had bought off recently, and one of them kindly sent me his address. Once he knew that I knew where he lived, and that I wasn't all that far away, I got my money back.