Who are the backup studio singers in the opening scene of Love Actually?

The backup studio singers in the opening scene of Love Actually are the vocal group known as "The Tonsil Tone". They are a real-life group made up of well-known British singers including Jamie Theakston, Chris Moyles, and Joanna Taylor. The group was put together specifically for the film and provided the vocals for the fictional pop duo portrayed by actors Bill Nighy and Gregor Fisher.