O'Connor was born in London, England. He began his training in theatre, as a dresser at the Old Vic in London. After this, he worked in a costume house for six years before deciding to go freelance.
In 1993, he began work as a wardrobe supervisor on such films as The House of the Spirits and Emma, before becoming an assistant costume designer. In this role, he worked on various films, including Oscar and Lucinda, Quills, Proof of Life and was also associate costume designer on the film version of Harry Potter and the Chamber of Secrets.
After working as costume designer on several minor Brit...