I've only just managed to do a little more research on this song. The earliest broadside date in the Bodleian Collection is for two copies printed by James Catnach at some time between 1813 and 1838.

Searching the British Library, there are two potential candidates for the "Collection of Garlands" reference in the BL. These are.

Joseph Ritson's "Northern Garlands", subtitled "A Choice Collection of Garlands...", 1793 (an 1810 copy is in the BL).

J. Clarke "A Collection of Choice Songs", Stockport ?1800

The former may not contain the song, but I can look at it when I am next in the BL. The latter is described as "containing, 1. High Germany. 2. Mog the Brunette. 3. Vicar and Moses. 4. The Roving Lass."

In any event, if things check out, we have now got it back to circa 1800 and, if it's in Ritson, to 1793 ... before the Napoleonic Wars.

I'd better check!

Cheers!
Ian