Cottrell Boyce was born in 1959 in Liverpool to an Irish Catholic family. He was an undergraduate at Keble College, Oxford and then completed a doctorate in English, also at Oxford University. Prior to his career as a screenwriter, he wrote criticism for the magazine Living Marxism. As a result there was supposedly always a copy of the magazine on sale in the newsagent set of long-running British soap Coronation Street, while Cottrell Boyce was on the writing staff of that programme. After he met Winterbottom, the two collaborated on Forget About Me.

Winterbottom made five further films based on screenplays written by Cottrell Boyce, Butterfly Kiss, Welcome to Sarajevo, The Claim, 24 Hour Party People and Code 46. Their latest collaboration, A Cock and Bull Story, will be their last according to Cottrell Boyce, who asked that his contribution be credited to Martin Hardy, a pseudonym. He told Variety, "I just had to move on ... what better way to walk away than by giving Winterbottom a good script for free?"

Other film directors Cottrell Boyce has worked with include Danny Boyle (Millions), Alex Cox (Revengers Tragedy), Richard Laxton (Grow Your Own) and Anand Tucker (Hilary and Jackie).

Cottrell Boyce has been praised by, among others, Roger Ebert, as one of the few truly inventive modern-day screenwriters. He has spoken against the "three-act structure" and the "hero's journey" formulas, which are often regarded as axiomatic truths in the business.

In addition to original scripts, Cottrell Boyce has also adapted novels for the screen and written children's fiction, winning the 2004 Carnegie Medal for his debut, Millions, based on his own screenplay for the film of the same name. His novel Framed was shortlisted for the Whitbread Book of the Year as well as the Carnegie Medal. He adapted the novel into a screenplay for a 2009 BBC television film. His 2009 novel Cosmic has also been shortlisted for the Carnegie Medal.

In addition to Coronation Street, he wrote many episodes of the soap opera Brookside, as well as its spin-off Damon and Debbie.

He wrote and staged his first original theatre production Proper Clever at the Liverpool Playhouse during the city's European Capital of Culture Year, in 2008.

On 18 September 2010, he co-presented the Papal Visit at Hyde Park with TV personality Carol Vorderman.

He is married and the father of seven children.