OK - well things have changed a little. Thanks to Mary's interjection, I added the "Course Completion Status Block" and it said something like "no completion status for this course".
So I went back into the conditions defined for the completion of the course, where I told you earlier it said "Course is completed when ALL conditions are met", and opened up the next twisty, "Condition: Activity Completion". I had assumed when I looked at it before that because it said ALL in the first drop down, it meant "ALL the things listed in the next section". So instead, I tried selecting them all, to see if that made a difference.
Having saved this the "Course Completion Status Block" for my user now shows the following:-
I don't understand why it has "Status: In progress" if everything has been done?
If I view the course report that is in the "Course Completion Status Block" from the admin user's point of view it shows this for my two test users that have "completed" the course.
So I guess my question becomes how to get the tick in that final column. I'm assuming the badge assignment is driven off that column rather than the 100% complete of the course.
The phone rang at this point and took me away from my screen for 10 minutes. When I came back, and refreshed, the ticks were in the columns and the badge was awarded, so I'm all good!
So I guess the pertinent point that I had not grasped is that 100% completion of a course does not equate to "Course completion".