Uncaught Error: Module Font7x11Numeric7Seg not found

The App loader does something secret in the background to add the font module into the source file that is mimised - maybe ?

Yes, that's correct - but the IDE should do this too - unless you have some kind of internet connection issues? You could check the console in the IDE to see if it failed...

I have also uploaded the Font7x11Numeric7Seg.js file onto the bangle and this makes no difference

Upload to a file called just Font7x11Numeric7Seg - but again that shouldn't be needed.

var size = Math.floor(g.getWidth()/(7*6));

It's just trying to leave enough room for 6 characters of width 7 pixels along the screen width.