There's nothing guaranteed to get my blood boiling quicker than a cold caller, most especially one who seems to be running a scam. Since I moved to Lincolnshire I have noticed a distinct increase in the sorts of PPI, you've had an accident, how's your loft insulation? calls. I'm not at all clear how these work, but when challenged for company names and details the callers invariably ring off.
I'm registered with the telephone preference service, and I regularly report people who call me repeatedly. One would have thought that BT or other providers might be able to tell if a company is operating a somewhat dodgy operation: if they are making dozens of phone calls and choosing to withhold their number, I would have thought that technology had advanced far enough for BT to be able to isolate the number and run some checks on the company.
One company which didn't withhold their number was Charter Legal, who have phoned me more than once despite my pointing out I am registered with the telephone preference service, and despite promising to remove me. They appear to be offering some sort of ringfence to protect your assets against the government - at least that was what I understood from their cold caller girl. Their website actually states the opposite.
In general, though, the companies which do this sort of cold calling are virtually indistinguishable from the bogus callers who claim to be policemen with your credit card details or Government researchers wanting to know if you have claimed your pension rights/PPI repayment etc. I'd ban it, and put fines in place for those who carry on.