The SC judgement makes that unlawful.
You cannot say this is open to those born female and those who identify as female. Because in law those males who identify as female are male in all circumstances with no exceptions.
Those females who identify as male are female in law in all circumstances.
Even a Gender Recognition Certificate doesn’t change your biological sex in law.
Service providers where they provide men or women only services have to provide them based on biological sex.
So regarding the ponds, it’s male, female, and mixed sex or all three have to be mixed sex. Simple!