Thanks.
I have checked the system and can see some changes. For example an issue I had with the update notifier system has gone away (but that could simply be because some old templates are not currenty on the system). I am therefore fairly sure it upgraded.
To close this I have to admit some embarrassment. I did wipe the system and clean installed.
I used Etcher in place of Rufus. It verified the image written was good - but then failed (informed that it had failed). So I swapped usb sticks and the thing worked fine. The original stick had contained another image which I had been using without problems so I committed the sin of “assuming” that it was good:-( - I believe someone in the forum had previously suggested that the problem was probably a corrupt image or bad usb stick!