The old theater I would go to sometimes ages ago, built in the late 40s, had a room right outside the auditorium just to the left of the left aisle (as you’re facing the back of the theater). You’d pass thru the double doors, hang an immediate left, and open a single door. There were about four seats inside with a plate glass window facing the screen and, I assume a speaker inside. I never noticed it used.
No, it was the norm in the UK too to come into the cinema at any time and stay for as long as you liked. I think it started changing in the 70s. It was so common a practice, in fact, that the phrase “this is where I came in” became current and used in other situations. We often missed the beginning of the movie and sat through to the next showing to see it (the double bill was standard then.)
I wonder if this change had anything to do with the de-institutionalization of the mentally ill and corresponding increase in the homeless population? I could see the price of a matinee ticket being an attractive option during inclement weather.
I had forgotten that the theatre was air conditioned and most everything else wasn’t. Even the stores weren’t. I recall only 7-11 having A/C when I was a kid.