People - well, women, I don't know what happens in men's toilets - being challenged when entering toilets is nothing new; it's been seized on now - as if the TRA movement really cared about butch lesbians and gender-non-conforming women🙄
In the past the challenge has been on the assumption that some bloke took a wrong turn and has blundered into the ladies'. 'Excuse me - this is the ladies'! usually resulted in embarrassed bloke apologising and leaving.
Occasionally, 'Excuse me - this is the ladies'! resulted in the gender-non-conforming women - me, for instance - replying 'It's OK, I'm in the right place'
and the second glance, and the tone of voice, reassured the women that it was OK and I was in the right place.
'Excuse me - this is the ladies'! has only become problematic since men started deliberately accessing women's spaces, where they know damn well they are not supposed to be.
'Excuse me - this is the ladies'! is nothing new and was no big deal when the good men stayed out so the bad men stood out, and it's obvious that TRAs and their allies are using it cynically as a way of undermining the SC ruling and EHRC codes.
The most straightforward solution is for people to use the toilets designated for their sex, which able-bodied transpeople can use, they don't need adapted toilets; they choose not to use the available toilets.
Disabled people are only entitled to 'reasonable adjustments', and the definition of 'reasonable' relates to things like practicality, disruption, impact on other users, and cost.
I think the provision of gender neutral toilets everywhere, for such a small percentage of the population, fails the 'reasonableness' test.
The building regs [for England] seem to back this up - there is no requirement to provide 'unisex' toilets. As long as there is enough space in a building, separate men's and women's toilets must be provided. Gender neutral/mixed sex/ unisex/ toilets may be provided, but as an optional extra.