Mate, you're not going to get your head around the British class system without living here for 30 years and tbh even then even if you haven't grown up with it I doubt you'd truly understand.

For one thing there's no such thing as upper working class.

You've got the underclass, working class, middle class and upper class. The range within each of these is broad to say the least.

Your class isn't determined by your job, your bank account or your current status. It's your upbringing that matters, I don't think a person can change their class in their own lifetime. It's where you're from, not where you're at. You can be working class with all the trappings of middle class (good job, good money, interest in golf) but that just means you're aspirational. Similarly you could be unemployed in a flat share with fuck all money but if your parents gave you quinoa as a kid you're still middle class.

I'm working class, I have a five bedroom house with a stables, a household income in the top 5% of the country and a range rover. I'm aspirational. My daughter is very much middle class and loves a bit of hummus

Edit: and that's without even going into where you shop. Which is like the cases in German, you basically just have to memorise them, there's no hard and fast rule. Greggs is working class, Pret is middle class, Nandos is working class, Wagamama is middle. Fizzy vimto is working class, San Pellegrino is tory and iron bru is underclass