@SmokeyToo I think that @MiddleParking is just being pedantic.
If your background is not upper class, then in the UK I think it is kind of true that you are not upper-upper class, because you generally have to be born into money, preferably several generations of it (unless you marry into the Royal Family which seems to be the only shortcut!), in order to be considered truly upper class.
And unless your parents are both died as soon as your private school was paid for, it was not literally a “lifetime” of hard work and sacrifice.
But I think anyone who read you without a pedantic mindset will have understood, and probably agreed with, the essence of what you wrote. I, for one, certainly understood and agree!
Congratulations on having made your way. It can be more difficult to navigate life as a “class traveller” but if you are kind, empathetic, and of good character, while also keeping a healthy unwillingness to tolerate too much bullshit, it helps a lot!