There's no evidence that the waltz "drifted into tradition" until it was published in Vic Gammon and Annie Loughran's The Sussex Tunebook in 1982, and got taken up by various people. Michael Turner didn't provide a name for it in his MS book, but it's German Dance no.2 (Trio) KV 536 no.2, 1788. Score (pdf) and midi renditions are available at

http://www.folk-network.com/miscellany/index.html

The MS version is a little different, but not much; it looks as if Turner heard it at the local Assembly Rooms or some such, went home and wrote it out from memory; accidentally incorporating a little of the second violin part into the melody line.