Oops. Forgot that Robin is in America. But Robin being Robin, he carries this stuff around in his head and has sent me this:

Blodeu'r Gorllewin
Parry (Ddall) Rhiwabon, John, British Harmony (London, 1781)
No background (or translation of title for that matter) appears in this volume.

Tune reappears in:

Jones, Edward ('Bardd y Brenin'), The Bardic Museum (London, 1802)
Blodau y' Gorllewin. - The Flowers of the West.
No background again.

Both versions markedly different from Playford's The Glory of the West but they are all the same tune in essence.

(Ddall means Blind - he was a blind)

Crowdercref has now played it me on the piano (ain't telephones great?) and I've decided I probably don't know it, although the closing phrase is annoyingly familiar ...

sian