Progress, finally!! Logitech support have solved the navigator problems but there are still others to be fixed that learning does not.
So, I'm optimistic all will finally work for the Harmony One.
The basic problem is not hardware as both Harmony One remotes I have behave identically. It does seem there is something odd about the Vu+ remote codes because, as I posted above it was similar problems before with a URC 850 (Aeros) that led me to change to the Harmony One. For some reason odd Vu+ codes do not transfer easily under "learn" functions. I'm guessing Logitech support are changing their No 1 Vu+ code set so it transfers across to the Harmony so it is without problems and no lerarning is required.
I had looked at getting another remote but there are limited offerings and i found none besides the Harmony One that have 3 important functions for me - 1. Number buttons (needed for play skipping but missing from many new offerings), 2. Backlit keys and 3. The facility to program macros (sequences using Harmony language). I'm not interested in controlling other house items & am happy to live with IF.
So, bottom line is to praise Harmony support. Great service can be hard to find these days, particularly with big companies so my experience with Logitech support is very gratifying.
An audio nut for over 60 years & now a video nut too :-)