James Corden

Character: Paul Potts

Alexandra Roach

Character: Julz

Julie Walters

Character: Yvonne

Colm Meaney

Character: Roland Potts

Jemima Rooper

Character: Hydrangea

Mackenzie Crook

Character: Braddon

Trystan Gravelle

Character: Matthew

Sion Tudor Owen

Character: Choirmaster

Alex Macqueen

Character: Dr. Thorpe

Miriam Lucia

Character: Signora Fiorentino

Stanley Townsend

Character: Luciano Pavarotti

Di Botcher

Character: Nurse

Jon Wennington

Character: Talent Show Punter (uncredited)

Owen Hunte

Character: Friend in Bar (uncredited)