1. Class has nothing to do with wealth or income and everything to do with behaviour, values and aspiration.
2. There's a clip on Youtube of a stand up comedian. He asks the audience to put their hands up if they consider themselves to be middle-class. Barely anybody does, so he points out that they are sitting in a theatre in Glasgow on a midweek evening, so why the reticence?
3. Nowadays everybody is so determined to appear "right-on" that the lines between classes have become meaninglessly blurred. Here we all are desperately trying to pretend we're all working class that we forget that the landed, moneyed classes used to look down on the middle classes. Surely by traditional definition the middle classes were the ones who lived in the town houses or commuted into the city; office workers, merchants, clerks, managers, possibly earning enough to enjoy the arts and the restaurants, and a grammar school education for the kids, whereas the working man worked in industry or transport etc.
What some people on here are describing as "Middle class" are actually either arriviste, or the nouveau riche. Then of course there is the Upper Middle Class. For them there is the land, the family money, the "breeding", the schools, the "old-boy" networks, the society calendar and invitations. It's no accident that you can tell how someone has been brought up by watching them eat a meal for example, or by the fact that they don't go into a panic if they are invited to a black-tie function 'cos they'll have to go and hire a suit, and agonise over whether they should wear a wing collar shirt. If it comes naturally, then that's breeding. If you have to buy GQ or Tatler to learn how to be a "chap" or name your baby then you've already missed the bus. Or was it the shooting brake?