I think the problem Jim is two fold.
1) Signage isn't a trivial issue but it is much lower down on the list of priorities when it comes to other fire precautions
2) There isn't any overwhelming evidence to demonstrate that the signage is not being understood
I was responsible for managing fire safety at a site with multiple risk buildings, some had the so called euro signs, some buildings had BS signage, and some even had the HTM style signage.
I even printed off my own signs from time to time too. The signage wasn't drastically different. They were always the same colour (green for exit signs) with directional arrow, a running person, and a door in all examples.
When I used to do staff and visitor training , which included foreign nationals, they all understood the signage. So... I don't fully understand where the confusion is coming from, and whether it is such a big problem in the scheme of things.