Yeah, there is a middle ground between "ignore" and "open the door and invite a can of whoop ass into your home".
I'll give you the sensitivity in the Chesire area (though I can tell you, it hasn't extended up this way) but that is a sort of individual thing.
I do know that the world has changed in other ways; when I was a kid, you didn't call after 9. You didn't ring the bell after dark. It was sort of a 'respect' thing, and as a result things had their own code. Phone call at 11:30? You answered it, because it WAS bad, important news. Knock at 10:30? You answered it, because it WAS someone in true need. Nowadays we've trampled, obliterated those sort of norms - and in some cases it is a situation where the scumbags among us have abused and violated those norms - so that you have circumstances like this.
it also depends where you live; in Philly, many of the row houses have intercoms, so you can have the sort of conversation that needs to be had to figure out what's what, though even that isn't fool proof, because if someone wants in your home for nefarious reasons, they are obviously not above lying to you through the intercom. There it was easy because I could poke my head out on the second floor balcony.