All, Now here was I thinking that Flowers of the Forrest was a tune in its own right, a wee Scots lament.
Anyway by far the best version you'll hear is by Kelly's Heroes, of whom I have mentioned before.
I always play it in G, as BK says, the chords are so easy.
Having talked about this to a friend at work (where I'm supposed to be now), he swears he has a version of it on some compilation CD, entitled William McBride.
Cheers
Mick