Jane Horrocks is a revelation in this touching story about a timid girl whose mother (Brenda Blethyn) is dating a sleazy talent agent (Michael Caine). Horrocks has an imaginary friend for whom she has a habit of singing, is overheard by Caine and he determines to put her on the stage. Blethyn is great is the venal mother, and Caine equally unscrupulous as they both try to exploit their shy charge. Her only salvation in all this is her friend "Billy" (Ewan McGregor) a local pigeon fancier who proves to be her true friend as she struggles with all the pressure. Horrock's own performance is…