Then this is much simpler.
First you need a decent broker. Hopefully you have a half decent one. He needs to turn the screw a little & remind him it is a legally binding contract. Hopefully with a little reminding by sedo you will get there.
They can then release their details to you from there i believe. They may be on whois anyway, if no privacy guard.
From then it's legal, depends how far you want to go, but eventually surely you would win.
The only hole i can see is if you took a long time to pay. The seller could argue if it was outside the 10 day period etc, but tbh i haven't studied the smal print
all the best
Pred