Banged on my door a couple of days ago. A little persistent although polite.
Weather permitting I always answer these people from my balcony that sits high and to the side of the front door. This tends to put them off their patter a little. I also have a good quality camera recording all video and sound from inside the porch. With another camera watching the road and garden outside the house for a good 60 yards eitherside of my driveway.
The most I will ever do is talk to them from inside the porch with the outer door locked.
My suggestion to most would be - do not interract at all or just answer from an upstairs window and say you are not interested whilst staying polite and courteous.
Call me paranoid if you like, but at the end of the day I have it all on high quality video if required.
Another scam is the amount of money we pay for policing!