lifesabeach "we have spaces for those with disabilities and that was entirely achievable "
I wouldn't describe it as entirely achievable. The battle for disabled access is a long way from achieving it's necessary aims, even after all these years, all the lobbying, all with the sympathy of the vast majority of the population. For example, inaccessible buildings being used for work capacity assessments by the DWP - and that's just to permit someone to get into a building to which they are required by agovernment department to go, never mind toilets or changing facilities.
Even if a third space were found to be an appropriate response fo the UK, the timescale to bring that's into reality as a useable alternative would be very very very long, most likely unsupported by a lot of people in terms of funding or the will to make it happen.
Imagine for a moment the government or LAs or other organisations allocating budgets to provide that third space. And bear in mind that right now all over the country businesses and charities and communities are fitting tooth and nail to have any public toilets AT ALL remain open in their area. In fact, now I come to think of it, all the public toilets in my local area (not a city) have gone over to unisex, and often there is a single accessible unisex cubicle, where before there were ladies, gents and disabled. Frankly we're glad to have any open at all having no gone through repeated stretches where none were open at all.
Interestingly, there is not legal obligation to provide public toilets in towns, villages etc, but that's another thread really.
In the meantime, a provision requiring third space would likely result in disabled facilities being co-opted or co-occupied as a compromise pragmatic position. In some cases where there is excess disabled provision that would be ok, but there aren't many places that fit that description.
I'm not saying it's a bad suggestion, just questioning the realistic implementation.