Result!
I'm always browsing for bikes on Gumtree and I spotted an ad last week with a ropey old description and a cock and bull story claiming that the seller had accepted a road bike for payment for a building job where the bloke couldn't pay in cash adding that his mate knows a bit about bikes and that it was worth £600. I didn't recognise the brand or the model so googled it and on 'images' the third photo was from a stolen bikes website. Via that website I contacted the person whose bike was stolen and I had two lovely e-mails from the owner; the first to thank me for letting her know and the second letting me know that she'd got her bike back! She's a cycle commuter and it made her day and it made mine too.
Result!