I got on the "do not call" list, available somewhere or the on the net I believe, and have received a total of 3 sales calls in the last 3 months. One of the callers is currently being prosecuted. But I live in Minnesota so your milage may vary. As for the door knockers there is a rule in America involving the posting of a "no soliciting" sign but iirc in the UK solicitors are lawyers rather than door-to-door salesman so I don't know. There should be something though