Mander's family has had organ builders in it since the 18th century. His own specialty was restoring, building, and promoting traditional, rather than electronic, pipe organs; he is listed in Grove's Dictionary of Music and Musicians as "among the first postwar organ builders to take what was then seen as a radical interest in Britain's organ heritage and the restoration of historic instruments."

In 1979, he recreated a late 17th-century/early 18th-century instrument, at Pembroke College, Cambridge, from its historic remains—the first-ever attempt to do so.