It's obvious that I forgot all about Peter Buchan's MS collection. I recently got Oswald's untitled variations on "The Lowlands of Holland" for the book of 1742 that Murray mentioned above. It's the tune that S. P. Bayard thought was the likely original of "Rosin the Beau". Incidently, I heard that from Scotland that Oswald's 'Caledonian Pocket Companion' is being reprinted in the near future, but I don't know by whom or when.