Downie's first professional film role was in 2002's mystery thriller Dead Man's Dream, from directors Abner Pastoll and Kamma Pastoll. Two years later he would star in director Emory Ruegg's short film Swiss Passport, which was created for the Straight 8 Competition at 2004's Soho Rushes Film Festival. That same year he would appear in the drama Shooting Shona opposite Samantha Béart. In 2008, Downie would once again work with director Abner Pastoll on his short film Homicide: Division B, a dramatic comedy about the British police, before starring in the direct-to-video horror film The Gatekeeper.
As a writer, Downie had his first theatre piece, The Dead Moon, commissioned in 2008. The play toured the UK and was also performed at the Aldeburgh Festival, the first non-operatic piece to ever be performed there. In 2009 he was one of two finalists selected in the Heat 2, first round assignments (of 540 entries in 30 heats) in the New York Screenwriters' Challenge for his script The Robin Wins The Spring. Since then his theatre work has included The Curse of Elizabeth Faulkner for 2010's Off Cut Festival in London, which was also performed at the King's Head Theatre, and The Revenge of Anubis. In 2010 Dowie penned The Story Project 2 – Love, Lies and London for The Southwark Playhouse and A Portrait of Maureen Flange for the Etcetera Theatre.