The Caledonian Pocket Companion was intended for deep pockets in every sense. The budget option in the later 18th century was Aird's books, which got everywhere and were very widely copied (witness the Village Music Project's manuscripts from early 19th century England).

But nothing like that was published in Britain in the early 1800s. Middleton and Cameron were first to produce cheap sizable collections, but nobody until Kerr published anything affordable with Aird's scope.