I didn't think the Unthanks were being intrusive with their song. The event was over and they were invited back to someone's house for a standard New Years party the way many of us are. They sang for their supper the way many of us do (or tell jokes, or show the white-eared elephant or the one-armed fiddler!). It brought the celebration back into the home showing it's not all about the public events but also about the private hospitality.