If you are endeavouring to see if your old vehicle is still on the road (whether from the noughties, the nineties or even from the nineteen thirties), one of the best and most authoritative things you can try is to get a RegArchive vehicle report. Priced at £17.00, you can receive a full report that gives you the best possible chance of finding out if your car is still on the road, and mechanisms for how to get in touch with past and/or current owners in a lot of cases.
You can find the vehicle reports here.