My DP immigrated here as a child, he said he found it hellish at first. 6 years old, no English, behind in school because of later start in his country. Went through a stage of Anglicising his name, denying his birth culture. Only child so very lonely as well.
So he can ‘pass’ as local as has the accent, but he still feels ‘other’ because he went home to a different language, customs, cuisine, every night. Doesn’t know if he thinks in his first language and translates subconsciously or if he now thinks in English. I’ve noticed he swears in his first language if he eg bangs his head and if you wake him in the night he’ll speak in it first. So still ‘other’.
He thinks on balance he’s benefited by belonging neither here nor there, but a lot to both. He also thinks he’s benefited because he’s a white well educated man. He has EU citizenship as well as UK, he has a second culture that British people are interested in and aren’t suspicious of, he’s a success here and clearly a net contributor, he’s an “acceptable” immigrant in other words. Sad but probably true.
He also pointed out he’s been a further ‘immigrant’ when he moved to another of the 4 countries in the UK. Had exactly the same dislocation and sense of not belonging. Wrong accent (uk one), cultural holes, assumptions made about him. So you don’t need to go far to be foreign.