I think there are more obvious markers of what makes someone NOT MC. ie A rich home owning, uni educated who speaks in a broad accent with lots of slang/swearing will not be MC.
Other WC giveaways are talent show watching, laughing at crude comedy, only reading supermarket fiction, hair extensions, not caring about education or discipline, lots of visible tattoos, thinking that a uni education is an achievement rather than what is expected, limo parties, english breakfasts in acky resorts, having multiple DCs at a young age, getting into debt to pay for expensive presents for DCs at christmas, missing teeth, wearing tracksuits other then at the gym, burping in public and thinking it's funny.
But on the other hand all this trying to look for ways to divide society is really just a ruse for poor people bashing. Everyone wants to be MC because society pours scorn at WC values.
I dont even think there is one MC. I remember from Kate Fox's book that there are distinctions between lower, middle and upper MC. eg Kate Middleton was upper MC which is a long long way off the lower MC people who probably tick the MC boxes in their generation but came from WC backgrounds.