Blame the Dog, she woke me up at 4.20am with Birds singing like they had gone Bananas.
So I went for a Fag in my shed, and a cuppa. Looked at my Picture of 'The Silver Tree at Lock Lomand' and suddenly had this blinding flash of ... doh, ... That's what I have been looking for. Wrote it down quick on an old scrap book, and legged it up here to write it up (reasonably) coherently.
See what you think if you ever find it.