I have a sticker on my front door. It's right at eye-level, so you have no excuse for missing it. It says "No Cold Callers. Please do not knock." There's a second, less polite sign, in the window to the left of the door, specifying that I don't want to be disturbed by salesmen, canvassers, hawkers, charity representatives or god botherers.
Despite that, on Monday, someone from SafeStyle UK knocked, and then apologised when I pointed out the sticker, and then said "but seeing as you're here now, can I just ask you...". He was really surprised when every question he asked was met with 'No'. His parting shot was "If you just let me do a quotation, you don't have to buy anything, but I'll get a commission." Strangely enough, my answer to that was also "No", as I shut the door in his face.
I know times are hard, but I really really object to doorstep sales. I will never ever buy anything on the doorstep and it really annoys me when chancers ignore the sign, in the hope that I'll be nice to them.
It is now a criminal offence in the UK to ignore such signs. I WILL report you.
Take a hint. Get lost.