Usually a certain area, maybe an estate, but not usually a street which contains the majority of old people. Another common factor, and most certainly of the one in Leeds, is the area is full of bungalows, also associated with older people. The name comes from 'angel' as in meaning 'dead', and 'island' as in meaning the 'area'.
Minnie: Down Angel Island, how about yours?
Mickey: Down Angel Island too. They're having a pensioners bash this weekend at the church hall.