Thanks for the reply, I had exited the beta programme but the updater still insists
"Your Mac is up to date -- macOS Cataline Beta 10.15"
If I try and install the public Cataline release from the Appstore the update runs and says "up to date" or "update not found" depending on what advanced options are ticked.
If I try and install a downloaded Combo update it says
"macOS Catalina 10.15.4 Update can't be installed on this disk. The volume does not meet the requirements for this update"
Same for 10.15.1,10.15.2 and 10.15.3. The machine is a iMac, late 2015 and the stuck beta macOS is 19A487l.
If I hold down Command+R to the recovery OS and install from MacOS Utilities screen it says the volume is not compatible. I also have the issue that both the keyboard and mouse stop working when it gets to the recovery utility itself.
I am backed up to the Time Machine but that seems to have split the last two backups from the previous series going back to 2016 which is another worry for restoring from the TimeMachine.
I presume the beta updates have to be applied in a certain order but since the older updates are no longer available the updater will not accept any other version - I just need to push it on. I was hoping someone would know how to change some internal flag the updater app is using.