the thing is, it’s not about the law.That isn't actually correct. but I don't want to turn another thread in to a legal argument. Sufficient to say employers have legal responsibly to provide separate spaces for males and females.
there is no way for a clothing shop to know if a trans women goes into the changing rooms
the only possible way would be if every woman had a gender identity certificate and a security guard checked every single person as they went in - never gonna happen.
employers may have a legal responsibility, but changing rooms have customers not employees