In properties of the metaball, I can change the number of the ball type but the look doesn't change. It remains a football. Is this because I'm using Blender 2.79 or could it be due to something else?

You most likely have an error at the top when you open the file.

Click "Reload Trusted" and it will relaunch w/o the drivers being disabled.

Also make sure you have 'auto run python scripts' checked in your user preferences.

(User Prefs> File > Auto Run Python Scripts)

From Alison (replying to the email sends a message to support - we haven't integrated email replies into the site just yet):  

Thanks for replying. When I first open the file, there are 2 pages: The first shows 01 in top right corner on a white rectangular background. This area is over a grey space with the football in the top left-hand corner. No menus visible (unless I click on any one of the 3 +s ). I close this to see a more usual type page beneath. 

That page had Autorun disable and reload trusted at top. I clicked on reload trusted > Ok? Revert. The first screen reappears. I closed that. I see a blender page beneath. I select the ball. Under Item is just Ball_2_plainball. 

Now there are not even any numbers to choose from, and certainly no different ball types. 

I then went to user prefs > File > Auto run Python Scripts I selected and closed that box. This seems to have made no difference. No other types of ball available. I don't have a Multi-ball UI panel. Even when I enable python scripts first, and save that, and reopen the file, and run python scripts: this no longer shows 'Autorun disable' but otherwise seems to make no difference.