Well the Public Entertainment Licence requirements, if stricty applied (give the time) mean that in England and Wales it's illegal to sing in any public place, apart from a pub (if there's no more than two of you) or a church, unless thgere is a licence in existence to cover it.

Maybe they'll come up with the idea of selling people individual licences which would entitle them to sing in other places too. Or even allow them to whistle as well.