Also, I have read that Hugh Webb's music has been used in television programmes and I strongly believe that one or two of his beautiful harp solo pieces were used in early episodes of the UK show Long Lost Family. All of the music is uncredited for some reason.

I just watched some of the videos of harp versions of The Ash Grove, and one or two showed double strung Welsh harps. That's the way to avoid the flipping levers, but I don't have that option. I'm guessing it might explain why my other fave Welsh harp tune (i.e. David of the White Rock) has accidentals as well.