Mylan is best known as Oliver in the television sitcom Coupling (2004), Chris in Grownups (in 2007 and 2009) and Joe Andrews in BBC Wales drama Belonging (in 2006). Other television work has included the role of Danny Flint in Where the Heart Is (in 2005 and 2006), Harry in Wild West (2002-2004), Border Cafe, Ben Phillips in Bad Girls (2004-2005), Leroy Jones in The Bill (1998-2001) and Doctors (as Dr Simon Hills in 2004 and as Will Duncan in 2010). He appeared in the 2009 film City Rats. He also made a guest appearance in TV sitcom My Family in 2007. He played Simon Lowsley, the deputy headteacher, in Waterloo Road until 2014. In 2014, he was cast in The Frantic Assembly performance "The Believers".