Thanks very much!
Its been rather too long since I stared at code for hours! Was driving me batty!
I've hacked even that version around as I want my logo to be an exact offset position from the bottom right hand corner and not derived from a percentage of the image size as this will vary on portrait vs landscape (or, god forbid, if I start using whacky non 2:3 aspect ratio crops!)
Perhaps if you are looking for other suggestions, then perhaps a way of setting such a hard pixel offset from each of the corners, all selectable with variables.
If I hadn't gone so code blind, I'd offer to code it myself, but my bodged version is too nasty to share