And this is a problem because?
It's not a problem at all, because nobody is going to be discriminating on gender reassignment as regards toilet provision. It's not even possible. It has been made crystal clear in the judgement that people go men's or women's depending on their actual sex. Gender reassignment doesn't come into it. There will be no court cases "legislating" about this, because it is already a done deal. It has been established that requiring males to use the men's and females to use the women's is
not discrimination.
There is no requirement to provide separate male and female facilities, but in practice that really just applies to very small businesses, which may only have one toilet to do everyone, single-occupancy with all facilities behind a lockable door. If they have two of these which were labelled male and female they may opt to make them both unisex but that would be no big deal.
The issue is large establishments with the usual separate Ladies and Gents with communal washing areas, with the Gents communal area also containing urinals. These usually also have a disabled-equipped unisex toilet. There is no reason at all why these should not continue as they are, and maybe turn a blind eye to non-disabled trans people using the disabled space. I suspect that's what will happen. We have seen some very woke establishents change the signage on their regular toilets to curry favour with the trans lobby, and this has caused much disquiet. The Donmar Warehouse and the Mermaid Theatre spring to mind. Since this seems to involve leaving the Gents as it is and relabelling the Ladies as being for everyone, I would have thought a claim of sex discrimination would be appropriate. Up to the clientele I suppose, but we may see that happen.
What I do not expect to happen is for many other establishments
now to try to change their normal toilets to mixed-sex. The tide is most definitely turning and women are getting tired of it all. If an establishment labels its former Ladies as mixed-sex and leaves the Gents as men-only, that's a definite case of sex discrimination I would have thought. If they simply label
both as mixed-sex, ditto. Women are going to say that they are
de facto prevented from using a space where men are using urinals, for reasons of decency and propriety, therefore they are being treated less favourably than men. If any litigation happens I would expect it to be around this point.
If the establishment tears out the urinals so that it has two cubicle-only mixed-sex spaces the men will be furious, and furious men tend to be listened to. Only the most terminally woke establishments are even going to contemplate pissing off the bulk of their clientele like this. Remodelling the Gents to get rid of the urinals and attracting the ire of pretty much everybody is unlikely to be a popular suggestion. Trans is on the wane anyway. The younger generations growing up think it's a load of performative bollocks, and now that a declaration that one is trans doesn't give a man an all-access pass to women's single-sex spaces I predict it's likely to get significantly less popular as a lifestyle.
Another area that may arise in terms of legal action is where a male enters the female space and refuses to leave when requested. I think that might throw up some interesting scenarios, and that's the space I'd be watching. But nobody, nobody at all, is risking "discrimination based on gender reassignment" by leaving their toilets as male and female, and being prepared to enforce this if necessary.