Westwood's first publication was in the weekly English music newspaper Record Mirror, where he worked for three years until 1981 and became the first English rock journalist to cover the work of the Irish rock band U2.

His first novel A Light In The Black, was published in 1989 by Penguin Books and became a runner-up for The Guardian Children's Fiction Prize. His second young adult novel Calling All Monsters (1990), had film potential and was considered for adaptation by Steven Spielberg's Amblin Entertainment and later Dreamworks,. Westwood's other novels include Brother of Mine (1993), a study of sibling rivalry between twins, Becoming Julia (1995), a taut thriller about a murder victim and her doppelgänger. These were followed by his cyberspace adventure Virtual World (1996), which was set set in a world of interactive computer games. This book was in included in the contenders list for the Carnegie Award.

His Internet stalker psychological thriller, Profile, was published in 2009. The main influence for this novel was the Alfred Hitchcock film Shadow Of A Doubt, one of several Hitchcock films referred to in the novel.

Children's Books;

• A Light In The Black. Harper Collins (1991). ISBN 978-0-397-32487-3
• Calling All Monsters. Penguin (1992). ISBN 978-0-14-034421-9
• Personal Effects. Viking (1991). ISBN 978-0-670-83879-0
• Brother Of Mine. Clarion Books (1994). ISBN 978-0-395-66137-6
• Becoming Julia. Puffin (1996). ISBN 978-0-14-037031-7
• Virtual World. Viking (1997). ISBN 978-0-670-87546-7
• Profile. Lulu.com (2009). ISBN 781-40928-848-0

Adult fiction

• Dark Brigade. Headline (1991). ISBN 978-0-7472-3479-1
• The Silence. Piatkus (1993). ISBN 978-0-7499-0195-0
• Sight Unseen. Piatkus (1994). ISBN 978-0-7499-0235-3

Short Stories

• Closeness, anthology: Thirteen More Tales Of Terror