Tell the police you will complain to the police commissioner with a formal complaint about how useless they are even when presented with the necessary information and that you will be sending a copy of this to your MP. Give copies of evidence and notes regarding any contact you have had with police if this does not get them into action.
Make sure you screen print anything from online as evidence such as the advert.
Lastly tell the f*****s that they will be sued for not doing their job properly for the cost of the replacement bike plus costs.
Police commissioner couldn't care less - by statute he/she has no involvement in operational policing. Most he'll do is walk down the corridor and slap the letter in a police officers in tray. Ditto your MP.
If you wish to complain do so in person or in writing to a senior officer. Alternatively, complain directly to the IPCC, although in most cases they simply pass the complaint back to the force concerned.
Do bear in mind that the police are bound by RIPA. They are prevented by law from simply ringing the bloke up, arranging a meet and then slapping handcuffs on him. A detailed application has to be submittted, which takes time and requires a high degree of evidential support. This is likely to include such things as a statement from yourself, photos or other evidence that the bike in the ad is yours, etc.
The only exception to this is where life of limb may be at stake, in which case the Supernintendo may accept an oral briefing and given an oral authority, but if anyone puts a floor wrong there they could end up in court personally liable for infringing some peace hippie's privacy.
Also they can not ask or encourage you to ring the bloke up and arrange a meet without a RIPA authority.
Also the police aren't liable for the loss of the cycle, unless it was stolen during a declared riot. Threatening legal action serves only to waste your time, make you look like a pranny, and get in the way of achieving your goal.
The obvious thing to do is phone in with your incident number, and find out which officer is dealing with your case. You can then quiz them as to where it's at. Be prepared to make yourself available to give a statement, and have to hand proof that the bike in the ad is yours (simply your word is unlikely to be enough) . He'll then have everything ready to get a RIPA authority, and then they can try and grab the feller, either by setting him up, or by obtaining the details of the subscriber from the website (always assuming he registered with his own details).
