Miles was born in Wimbledon, London, but lived as a young man in Ashover, Derbyshire, attending Tupton Hall School. He began acting in school productions, which he pursued mainly because it allowed him to miss classes. In an interview, Miles stated how he would spend his spare time in a now-defunct record shop (Hudsons) in Chesterfield, Derbyshire while "thinking about 'finding the one'". He trained at the Guildhall School of Music and Drama. He moved into television roles in the 1990s, playing supporting roles in such series as Zorro, Soldier Soldier, Is It Legal?, The Bill, Peak Practice and Wonderful You.