Born Clare Woodgate in Colchester, Essex, she attended Colchester County High School for Girls and broke into television acting when she was only sixteen years old, playing the role of the original Jenny Porter on the BBC's 2point4 Children. After two series she left the show to concentrate on acting in television drama such as Casualty and The Bill and in low-budget films.
In 1995, Cates (then still known as Clare Woodgate) applied for the role of Stella in the film An Awfully Big Adventure but didn't get the role. She returned home, dyed her hair red, and re-invented herself as a 17-year-old Liverpudlian girl called Georgina Cates who had no previous acting experience. When she re-applied for the same role, the casting director hired her. She went on to co-star in such films asFrankie Starlight (1995), Illuminata (1998), and A Soldier's Sweetheart (1998). She received critical acclaim for her role as Amanda in Clay Pigeons (1998) with Vince Vaughn and Joaquin Phoenix. After a seven-year break from the movie industry, Cates returned to the independent film genre to co-star in Sinner, for which she won a Best Actress award at the Brooklyn Arts Council International Film & Video Festival.