I'm not going to spend the rest of my life exlaining every single EU regulation to people like you. For a start, I don't know them all, I leave their interpretation and application to professionals who get paid for doing just that.
BUT I'll just do this one. The UK has the power to repatriate any EU immigrant who does not conform to the rules concerning work, pay, health etc, after 3 months. The UK chose not to bother its arse (as carbon rod already said)
So you were obviously unaware of that. What else don't you know? Do some research instead of parroting shite from the like of the Mail, Sun, Telegraph, Express etc. These organs all have some vested interest in brexit. You, if an ordinary working guy, do not.