In the ebay description, he has nothing written about also having it for sail outside of ebay. I'm sure that means he doesn't have the right to withdraw it, sell it to someone else or cancel the sale through ebay. And also, he didn't set a reserve, so seeing as that is what it went for, that's all you need to pay. Contact ebay, and if he still refuses to sell, ebay will take disciplinary action. Sure, it may only lead to him not being able to have an ebay account with that e-mail address/details but it's what he deserves if he's going to mess you around and not play by the rules.
Hope you can get it sorted!
Max