I agree with SG.
We used to have JW's come witnessing where I used to live. I would thank them for their time but tell them I am not religious and that they didn't need to visit me anymore as I would seek out religion in my own time. Because there are loads of different groups that would witness (not the same people everytime) I had to do this a few times but eventually they stopped coming.
I really dislike door to door anything... TBH, anything that invades on my homelife I find annoying, as like you Nic, I am most likely to answer the door in my PJ's with bed hair.