I don’t expect them to have fully assimilated into my culture, my family and my culture is Welsh, this is England, not the same. Generally in the UK it’s not considered particularly polite to ask your potential son in law about their past relationships or to divulge all their financial details, that’s pretty shallow. They’ve lived in England since birth and worked here all their adult life so I would expect them to be aware of certain cultural norms like being polite to people before/ when you meet them. I don’t think it’s a cultural norm, a friend of the same culture told me it is only somewhat more common in that culture but only because of how strict and controlling the parents remain of even adult children.
I agree it’s more to do with my girlfriend than anything. There’s an element of Chinese whispers at play here as I don’t know whether she’s been asked to convey the 2 last questions to me. I also generally don’t think she should have told me they asked these questions if she was clearly aware they weren’t ‘OK’ questions to ask in the first place. Also being annoyed at me for pushing back is not fair, it’s essentially saying I have to do/ say what her parents say and if I don’t she’ll be annoyed at me.