After much yak-shaving to make my UI library usable for other people I've finally made it public on GitHub.
It's very much a 'perfect is the enemy of good' initial release. It seems stable in use, I've written quite a chunk of documentation in Markdown and added an example for every widget type.
Now it's also been submitted to Arduino to see if I can get it listed in the Library Manager. If it is this will be a big milestone for me, giving back to the community.