Actually, thinking about it, they didn't ask me about any prof of "right to abide in the country" when I passed the driving test in the UK, they only asked to prove that I live where I said I do.

The accent yes - like neva_butterfly noted below, I know plenty of cases when older people's accent persists (still, it usually becomes intelligible enough), especially if people life in closed communities. But people who immigrated as children usually speak like natives by the time they grow up..