Derek Gifford's CD "When All Men Sing", Matthew, consists of Scowie's poem set to music by Giff, including as you say The Walling Song as well as the title song.

A relevant snippet from Giff's biography (link given above by Matthew):

A few years ago at the National Folk Festival someone entered the Traditional Singers' competition with the Walling Song announcing it as traditional. Thus Derek and Scowie now rank among the best 'traditional' song writers!