So both the items you bought caught fire? If the seller is registered with eBay in the UK you can report this to their local Trading Standards office. Or possibly even to yours, who may be able to pass it on. If the seller is regstered in another country they are beyond the jurisdiction of UK laws.
Your experience is yet another reminder of the risks of buying from unknown sellers on eBay. The user agreement did warn you that eBay does not guarantee that items sold here will be safe, or even legal. Would you buy from a shop that stated this? Think about it.
Also bear in mind that the sale is entirely beweeen you and the seller. eBay provides its own, limited 30 day guarantee for most items sold here, but after that they will not get not involved.