I think there was always one free one.
If you're in England the public washrooms like in train stations etc cost you from 30-50 Pence to use their facilities. There is always an attendant there and the places are kept absolutely spotless. There is usually the smell of a disinfectant there as well so you know it's clean.
That could be, it was 55-60 years ago so can’t remember all the details. But to this day that’s the only place I ever saw pay toilets. Remember thinking what kind of business would stoop that low to make money.