In British English, "middle class" refers to the well off professional classes or merchant traders.
In American English, if I understand correctly, everyone who works is considered middle class.
Class isn't tied to money as much as the US.
For example, I grew up poor (as in eligible for free school meals in the 90s poor) however I was one of the posher kids in the school. Class is fucking hard to explain definitively.
It's a most excellent insult.
You get the implied snobbery of an upper-class person looking down on their inferiors, whilst also maintaining some street cred via not insulting the painfully poor.
examples: "stupid middle class French boys" "god-awful, self-indulgent prose that only the most basic of middle-class housewives could appreciate" "a speech reeking of vapid middle-class cliches" ...
UK middle class also includes university lecturers, teachers, various health professionals, graphic designers and so on, most of whom make less than 100k USD/year and some not much more than 50k.
I don’t think it’s controversial to say that Oxbridge has historically admitted a lot of kids from quite a small group of high cost private schools. The fact they’re adjusting their intake to somewhat reduce that is something to be celebrated.
Unless you’re a very wealthy person with kids at an expensive private school in southern England hoping that they’ll get admitted to Oxbridge, of course.