"You don't have to show ID to buy alcohol, knives or solvents unless you look underage. Also, I've never been asked to show any sort of id to book into a hotel in the UK."
I get asked for ID every time I visit Scotland and stay in a hotel (or hostel), even at the ones which seem to be being very "British" rather than enthusiastically "Scottish".
"Last time I claimed JSA (a few years ago now), I don' recall having to produce id either (but I could be misrembering this)."
As I understand it, you can't claim JSA or any other benefit without your NI number, which is a form of ID. I certainly needed mine for the brief period I claimed JSA, but that was 20 years ago.