Legislation does not limit the "what" in any case, Roger. Anyone can sing any song without permission anyway, though most ask.

The "when" is always subject to causing a nuisance, but with a little common sense I avoid disturbing neighbours without feeling limited.

Finally, legislation might limit the "where" (unlicenced premises under certain circumstances) - but there are always alternatives. I certainly have not been stopped from singing anywhere, yet. Not on the street, not in friends' houses, not in gardens, not in churches or schools or hospitals or village halls or restaurants or coffee shops or Arts Centres.

There are always alternatives. Some may involve the hire of a room, where before one was had for free. But there are alternatives.