Hello, just to give an update, I was unable to change the database details in the Softaculous “edit installation details” area so as a workaround I re-exported / imported the database I wanted and that seemed to work OK. I have now tried to take the steps suggested in How to fix a corrupted WordPress installation kindly provided by @kangjl but now when I navigate to my site I see “Directory Listing”.
Incidentally I am now unable to make any changes at all in the “edit installation details” area, even just deselecting automatic updates gives me that same error message “The MySQL database name is incorrect as the database could not be selected.”
Just in case anyone has encountered or encounters in the future, the same issue.