I'm trying to figure out how the law works. I get that the equality act states in law that services etc mustn't discriminate against people on the basis of the 9 protected characteristics. That includes sex which is now clarified as being bio sex. And "gender reassignment " which in practice means self identified transgender. It can relate to provision of various things including loos, changing etc. If single sex changing wasn't provided for eg, this could constitute discrimination- so far, so good.
But couldn't it be argued that if only m and f changing were provided, then trans people are indirectly discriminated against under the equality act, because it would be unreasonable to expect them to use the facility for their sex?