'White trash' and 'chav' are habituses. (I know you have no f***ing clue what that concept means. It will take far more than a quick Wiki read to grasp it. So don't try to 'pass' as if you understand it.) It's all about culture, not money. Language, mannerisms, tastes of a particular class.
I was raised in an upper middle class home. I was indoctrinated into an upper middle class habitus. I could be homeless and I will still have that habitus. You were raised in a trailer then a foster home. You have a lower class habitus. You could win the lottery tomorrow and you will still have a white trash (lower class) habitus. Think of the show The Beverly Hillbillies. You can post a pic of me crawling in a dumpster and I would still retain more class than you in a pic in front of the Louvre. You can't buy a habitus you have to earn it. It is like religion, indoctrinate early. Of course there are those who are good at passing. But most can't.
Look at Katie. She looks posh, no matter the setting. She has an upper class habitus.
Is this posh enough?