I Want Candy is a British comedy about two aspiring film students who take desperate measures to get their first full-length film produced. Studying film production in Leatherhead, England, Joe Clarke (Tom Riley) and John 'Baggy' Bagley (Tom Burke) have grown frustrated at the limitations of their Professor Dulberg (Mackenzie Crook) who spends more time demanding compliments from his students than refining their creative expression. To make matters worse, Dulberg insists on arty, two-minute films rather than the theatrical film script they know will be a success.
Confident in their abilities, the two friends take a trip to London to meet with production companies and are summarily rejected until they try their pitch at Head Productions, where adult film producer Doug Perry (Eddie Marsan) is desperate to sign a star and sees the young men as a way to cement the deal. Doug offers to pay for the production if the two aspiring filmmakers can sign Candy Fiveways (Carmen Electra), the world's most famous adult actress, to star in their film.
Joe and Baggy jump at the chance to make their film, even though Doug will only pay for the film after it has been completed. They manage to track down Candy, who has retired from performing. Nonetheless, she agrees to make the film. With their limited resources, the students must find a way to make a hardcore adult film, using their college's resources. They manage to bring together a crew and audition a cast willing to keep their secret. They also have to resort to using Joe's childhood home as a shooting location with his parents Val (Felicity Montagu) and Stephen (Philip Jackson) innocently hosting the production.
In spite of their inexperience, especially with sex scenes, Joe and Baggy manage to complete the film, and receive a surprising reception to their work.