Well , thought I'd try to update again. Still getting no update available even though still on 2023 ( my standalone is now on 2025 ).
This time I had a long chat with Garmin technical support and was told that , as from Jan.31st , Garmin are no longer supporting the Honda units. Presumably this means only the ones over 5 years old . Not sure if just the Jazz but got the impression it was all models.
Gave Honda UK a ring to try to get more info. but , predictably , they know nothing about it.
So it remains to be seen if this is a temporary issue ( technical problem ) or permanent .