2nd hand car problem from ebay sale

I bought a 2nd hand car on ebay. After 2 days it began overheating, and when I took it to a garage, they found it had cylinder head/head gasket issues. I contacted the seller who denied any issues when he had it. Today I got the V5 back, and it says he was never the owner, but he says he was in the advert. So I have a problem with the heads, and the fact he was not the owner. Ebay are at best hopeless. Any advice on what I should do ?