At the age of 11, Kate attended the Redroofs Theatre School in Maidenhead, which she would eventually leave after completing her GCSEs at the age of 16. Her first job was an appearance in a Sugar Puffs commercial, dancing with the Honey Monster.

She made her television debut in the British television drama Shrinks (1988). She has also performed in a number of theater roles amidst her television works including Pandora in the musical Adrian Mole, Wendy in Peter Pan, Sarah in A Game of Soldier, and Geraldine in What the Butler Saw (in which she was nominated for the Manchester Evening News Award).

When she left Maidenhead, she landed a role on the British television sitcom Get Back, just eight days after completing her examinations.

Kate's big break would eventually come when she was cast as Juliet Hulme in the critically-acclaimed movie Heavenly Creatures (1994). She was working behind the counter of the Traiteur Pagnol delicatessen in Primrose Hill, London when her life changed. Her debut won her international recognition and awards, along with movie scripts from Hollywood in abundance.