I have had a good experience with this eBay store in the UK. Andy is the chap who runs it and he is a 100% guy who loves dealing in Modded genuine Seiko's, so there are some legit people dealing on eBay. But like you say, there are some dodgy ones to. I have reported obvious fakes to eBay and never had any response or thank you.....sellers just keep on selling!
http://stores.ebay.co.uk/mrvintagewatch/