Hampshire Police recommends this useful site
It has a section to check for bike serial numbers (for those thinking of buying to check if stolen) and to report stolen bikes too.
http://www.findthatbike.co.uk/ is a site that will send emails to the registered person to advise of any bike put up for sale on Gumtree or Ebay which matches specifics entered by the user. Anyone who has had their bike stolen can enter their bike details and any matching that are put up for sale will be sent to them by email.
