Update:
OK, I tried putting back in the non-working "video parameters" code (movie_rec.c) and can now see that "Enable optical zoom" is an option in there.
I can also confirm that trying to record a video causes to camera to immediately lock up requiring the battery to be removed to clear it.
So... my next question is "Is there a way to enable the optical zoom without enabling the other broken bits of code?"
I will have a look again myself, but my understanding of how all this hangs together is pretty limited.
