If you are implying that unlike other Western countries I've been to, in UK urinating and defecating in public is normal, then I apologize, I wasn't aware of that and stand corrected.
I'm responding to the linguistic markers and assumptions (for example, children-sized toilets!) that suggest you are either from the USA, or are from a third country and learnt US English as am additional language. If this is in fact the case, it would be a bit much for you to lecture me on "our" cultural values, wouldn't it?
It would go some way towards explaining your posts, which are most unexpected.
In my experience, I was generally the only mother who wouldn't countenance public urination behind bushes, and people certainly never took exception to the sight of a potty or a potette seat in the ladies.
I had a look at some offers and hopefully they will enable you to make the occasional visit to a supermarket with a nappy on (considering you are doing potty training, you don't need them at all times) and perhaps this could help? It's 11p per nappy so it shouldn't be too much, hopefully.
Not really relevant to me... Where do you think I got the figure of two years from? That's two years from point A, potty training at two years old to point B, four years old, when they were old enough to sit on a toilet seat without falling in.
But all things considered, if you had extended your kind googling skills when it was relevant, I would just have given you a cup of tea and a creme egg.
I don't see why a toilet-trained toddler should have to mess themselves and go through the clean-up just to save someone from the sight of a potty, I don't see why a family should have to buy expensive nappies to save someone from the sight of a potty and I don't see why a family should increase their impact on the environment to save someone the sight of a potty.
And if I thought toilet facilities were going to be lacking, I put my kids in cloth nappies anyway.