I have a bunch of .html files, just nothing loads in game, I see the same as the default.
I'm currently running both the default and my ui through an HTML formatter just so they are both formatted consistently so I have a slight chance of spotting differences.
It seems the converter uses the 'wall-o-text' format where everything is just one mass of text.
If anyone is interested, this is my ui:
NewAngUI
And this is the default:
NewDefaultUI