Having recently read in your Telegraph Motoring column of people suffering woe at the hands of canvassers I have just sold my 2002 VW Polo via www.autotrader.co.uk and didn't receive a single call from a canvasser. Autotrader has a free "safe sell" service where they replace your mobile number with a different one that filters out any calls from known canvassers. Granted this doesn't remove other potential pitfalls of selling a car privately (they do have an excellent advice section relating to this) but it did remove one unwanted headache for no hassle, and I would recommend it to others.