Working class is normally manual labour - i.e. plumber, builder, sparky

Middle class would be skilled labour - i.e. Doctor, Writer, Teacher

That’s kind of a guide line, I think there is a list somewhere that can tell you what bracket you fall in.

Its not that important anymore, I think they still use a similar guide lines to tell which TAX bracket you are in. i.e. a doctor pays more tax than a Labourer.