This was quite a useful guide on eBay that I linked to from my 'I was scammed on eBay post'. Unfortunately it's been removed so i've just copied and pasted it here from the Google cache. Originally written by eBay member groundhog.day on the eBay reviews & guides section with the title 'How To Complain To The Police About A Seller'.
It is an inevitable consequence of eBaying that from time to time you will encounter a rotten apple attempting to sour the whole barrel.
Although this is a relatively rare occurence it helps to know the best way to get the Police to take you seriously.
This is how I recommend folk approach the Police to report a seller they believe has behaved dishonestly.
The first thing to do is to ring your local Police station and make an appointment to see a CID officer - don’t frustrate yourself by arguing your case with a desk clerk in reception - they are programmed to dismiss cases of non delivery as civil matters.
When you attend the Police station you will need to have hard copies of any emails you have received in relation to the auction, if possible make sure these emails display the headers. If you don’t know how to make headers show - ask, they’re important.
Print out a screen shot of the auction you won and add to it your proof of your payment.
You should also make sure that you can supply the Police with the user names of other winners, together with the item numbers of all the sales. You are building a case that can’t be dismissed as a civil matter - bear in mind that third party emails won’t be able to be accepted. In other words, emails forwarded to one member from another victim cannot be considered as part of your complaint so don’t waste time gathering them.
The Police Officer that you speak to will hopefully be aware of the intricacies of eBay - almost every Police Station now has at least one specialist Officer with knowledge of the site - however it is possible that they won't be available.
Just in case the detective you speak to isn't au fait with eBay, bring the contact details on the following page with you - he or she will need them to contact eBay.
Once you have received a crime number be prepared to relay it to any of the other buyers who you are able to contact. They can add that information to the details they supply to the Officer who takes their report.
Whilst all this is ongoing you should, of course, continue with the relevant eBay standard protection claims.Finally - be realistic about what you are hoping to achieve.
The wheels of justice are notoriously slow but they do turn and they will get there eventually so don‘t give up.