It's utter bollocks to say that middle class people are insecure in who they are and are constantly eager to be something else. Some people are, yes, but I don't find a hotbed of insecurity and social climbing amongst my middle class friends. yes, a bit, amongst those with "lower middle class" backgrounds but the rest of them couldn't give a shit. They are who they are.
I was brought up in a working class area where it was virtually a crime to be middle class. The people I knew were fine, but from those I didn't know the aggression and jealousy could be overwhelming. Just a bad were the snobby working class mums who wanted their daughters to be friendly with me because I would be a good influence. So bollocks to the theory that the working class are all happy as they are. Not that they shouldn't be, nor should they feel they have to stay "in their place", but it's crazy to say they're all the same.
As it was such a poor area, mere middle class plebians like me also got to spend a lot of time with properly posh folk. I found, and find, the same mixture of people in the upper classes as I do in the working and middle. I really hate the disgusting spectacle of upper class girls throwing themselves at the most "eligible" man in the room, regardless of whether he is evenly vaguely pleasant. The plan for the girls, from the word go, is to marry as well as they can. And when women from different backgrounds come into the equation they are horrified. One of my (titled) friends did marry a girl from a middle class (but hugely wealthy) family. All the way through uni the other girls were constantly slagging her off, starting untrue rumours, and excluding her where ever they could. All the time they were flirting with my friend and trying to get him into their beds. When he married her, had children and was blissfully happy they were all amazed.