Help! What’s the title and author of this book/ series

[Caroline]

Fallen Crest High
A bit similar to Fallen crest series. YA book/series
Set in Britain. Girl sent to live with father she never met, new wife, stepbrother and half little brother.
They are well off and she goes to a posh school in South of England. She is northern. Stepbrother and girlfriend invites her to a party where she meets stepbrothers friend in basement of house. He’s well off- don’t get on at first then get together. Problem with his father...