As an actor, Welland appeared as PC David Graham in the BBC Television series Z-Cars as well as a villain in the 1970s drama The Sweeney. In films, he appeared in Kes (1969) and Sweeney! (1977) as Frank Chadwick, an editor of a newspaper, before also concentrating on screenwriting. He also appeared in the film Dancin' Thru the Dark in 1990. He also appeared in the 1980 series 'Cowboys' with Roy Kinnear, a comedy about a dodgy builder.
In Kes (1969), Welland had played an English schoolteacher, an occupation in which (like fellow Kes actor Brian Glover and its writer Barry Hines) he had been employed, teaching art at Manchester Road Secondary Modern school in Leigh, where he was known as "Ted" Williams because of his Teddy Boy curly hair style. Amongst his pupils was the future author John G. Sutton, who was once "slippered" by "Ted" for talking during school meals. Another pupil was Adrian Watson, who is now the Huddersfield town crier.