Mellor first came to the public's attention in 1990, when he played Ben Rowlingson in the children's programme Children's Ward. In 1995, he joined the cast of the soap opera Hollyoaks and played James "Jambo" Bolton until 1998. He had a cameo as Jambo in a Christmas edition of Hollyoaks. He released a cover of Leo Sayer's "When I Need You", which reached number 5 in the UK Singles Chart, as well as a follow-up single called "No Matter What I Do", which reached number 23. He also made an appearance in the music video for Boyzone's Comic Relief single "When the Going Gets Tough".