I've had a bit more of a play and now tried the Rev 2 with several other controllers and it is something strange with the controller keyboard I was using.
I was intending (and hoping) to use my Kawai K4 partly as it has after-touch and is currently sitting below the Rev 2. I wonder if there is something strange/antiquated with the MIDI implementation?
The hold button works as I would have expected with the Sub 37 and a Triton I have also tried as controllers.
I was starting to think something was wrong with the Rev 2!
Thanks again for your replies.
Best wishes,
Steve