Two points:
In Scotland in the 1950s we were taught that realise/ realize, visualise/ visualize were both correct. It was up to the user to decide which spelling to use, but that having made your choice you should stick to it and not use both spellings in the same text.
A lot of Scottish children were brought up to ask if they could go to, or use the bathroom, thus avoiding the controversey as to whether lavatory was rude and toilet polite, or the other way around.
Neither the s versus z business or the use of bathroom for toilet or lavatory were considered American usages.
As toilets are standard features of bathrooms, you were not left facing the dilemma if you had asked to wash your hands that I once did, as there was no wash-basin at the toilet, so I was shown to the kitchen sink and had in some embarrassment to say I needed to wee!