Their buyer feedback shows that they have pulled this nonsense before. So, no one will be buying the "honest mistake" story that they are selling.
http://feedback.ebay.com/ebaymotors/...All%20Feedback
I would definately fight to get the car. I would strongly suggest that you avoid using a lawyer, they will suck you dry (unless you have a close friend that will do it for free). The lawyers are the only ones that win in the legal route. I should know because the blood suckers usually get me for a few grand every few months.
The best course of action is to be pleasant and persistent. Keep accurate notes of detail, names, times etc. DO NOT get abusive or threatening. Keep the high ground because you already have it. They are the sleaze and do not go to their level.
Persist in your planning about negative publicity. This may be the trump card that gets you the car.
But in the end, we can all create new ebay accounts and screw-up all of their other auctions and effective end their ebay business, if you choose to go that route.