@TomJGooding I think this is the fix...

Wouldn't this introduce a new issue where the Select would stay expanded if you clicked to focus another widget?

You're absolutely right. Pushed an alternative fix, which doesn't break hiding the drop down on blur.

This seems to have done the trick from a quick test!

Just for my own knowledge, is this suppression of the click really only required because the 'overlay' concept doesn't play nicely with how the focus is handled?

Just for my own knowledge, is this suppression of the click really only required because the 'overlay' concept doesn't play nicely with how the focus is handled?

Pretty much. The interaction with click / blur was proving to be difficult to unpick. I suspect it could be done much simpler with pure CSS, but I didn't get that far.