I have thought long and hard about matters of class and family and I have come to the conclusion that it matters little what rules you follow so long as you DO NOT try to make someone else feel bad about it.
I am from what I consider a middle class family. My husband is from a working class background. No problem for either of us. We both believe in treating people with respect and kindness no matter what they do with their cutlery.
However, my DH's grown up son from his first marriage has spent a lot of time trying to make out that his family is incredibly upper class.
He is constantly making a fuss about forks and commenting on people wearing the wrong sort of tie. He tries to make out his family is landed gentry when they really are not - his mum once had a part-time job in Gap and his step-dad is manager at a local furniture shop. They live in a converted bungalow not a country estate. 
There's nothing wrong with that background whatsoever just don't try to make out you are something that you are not. He's like a male Hyacinth Bucket.
Can you tell it really winds me up? 
I've felt much irritation at his repeated one-upmanship at the expense of me and my family and even DH and his family.
Now I've realised that it doesn't matter to me if not-so-DSS wants to go round wearing a tiara and trying to pass himself off as royalty. What is unacceptable is using social mores to put me and my family down.
It's wrong to put someone else down to make yourself feel good. Using class to do that only highlights your own insecurity.
People with true class don't try to put others down. We know it's all about respect.