Here is a link to a site that has a map of UK toilets...
Here is information on an app to Worldwide toilets...
There is a good article on this link...
You can also google search Paris toilet map, Rome toilet map etc, etc for some countries around the world and have them at your fingertips when you go travelling.
I hope this helps and wish you the best of luck for your future in dealing with your paruresis.
P.S Fellow paruresis sufferer are sypmathetic to each other so don't be embarrassed any further.