OP, I know exactly what you mean.
I come from a pretty poor background, but did grow up in a ‘naice’ village in the countryside with a fair few ‘toffs’ for want of a better word. I had a pony at stages (when my parents could afford it) and went to YFC (young farmers) and was very good friends my whole life with a ‘posh’ girl.
Through the YFC and my friend I met some very posh people and ended up dating a very wealthy man when I was in my mid 20’s. He was 30, gorgeous and very very old money rich. I was pretty besotted with him....but my god, his family, his friends and their wives were just absolutely awful. Once they found out i didn’t go to private school and didn’t own 500 hectares, they didn’t want to known me. The women were awful, would just completely ignore me, I’m quite good at socialising and making conversation, I even knew some of these women through the local riding club so there was conversation to be had, but they wouldn’t entertain it. My ex said it was because I was pretty and they were jealous, no, it was because I wasn’t a braying snob with a title.
Him and I saw each other, on and off for 5 years, but I ended it fully 6 months before I met my now (lovely) husband as ex was ashamed of me. He’d never admit it, but he was and I knew I’d never fit in with his circle and didn’t want to spend my life miserable on the outside trying. I didn’t even WANT to be accepted by those awful snobs towards the end, it’s laughable.
I still see some of them sometimes and funnily enough they’re keen to say hello (as there’s no danger of me trying to infiltrate their precious world now) I just smile sweetly and sail past. A load of two faced, nasty bitches.
I’d echo the advice of the poster that said be PROUD of who you are and don’t try and ‘fit in’ they are more likely to accept you that way. Though my main advice would be to choose a partner who won’t let the women in his group treat you like shit. Choose a partner who isn’t immersed in such a superficial, snobby world.