I remember being told years ago by a GPO electronics wizz that detector vans didn't really work, they just drove abrround with a list of unlicenced addresses and knocked on any doors that had an arial and no licence.
I am being pestered about a disputed debt to Ebay. These people have phoned me a couple of times and the first thing they request is my security information. I simply insist that as they have called me it is THEY that should be giving me the security information, as they could be anyone, they refuse to give me any information quoting data protection. This also works a treat with sales calls from insurance companies, banks, mobile phone companies . . . . . . .