@oldfred thanks, that is what I will be looking at next, and I'm sure your links will prove a good starting point, when i actually get back on this project later today or tomorrow.
just a quick update: the surplus Windows8 boot option has mysteriously vanished, and Windows boots fine from the other (what I am back to for the time being, victory having been achieved concerning the hat). I don't know whether this was fixed by the third run of boot-repair (after partition resize) or what. The surplus ubuntu option remains. paste.ubuntu.com/5577256