OK!! I've disabled movie mode (I haven't altered movie_rec.c yet) and we seem to have a runner. All the basic OSD functions are there (battery, date etc) as well as RAW capability, zebra, histogram and script running. I don't think I'm going to have time to finish the job before I go on holiday next week as there are more than 600 addresses to recalculate, check and alter in movie_rec.c, and I simply won't have the time. (Unless of course someone knows of a program to do it automatically - I need to add a fixed offset to all eight character addresses starting with FF, then I can change the relevant few back manually.)
We're getting there!