"Toilets Matter" is a recently published "short guide to law and good practice" . It is a brief but comprehensive guide giving reliable advice to any organisation that provides toilets for use by members of the public. The guide deals with the often-misunderstood issue of single-sex toilet provision and design issues. Based firmly on the law, good practice and research carried out in 2022, the guidance is produced by Sex Matters, a not-for-profit company..
I think the information given in "Toilet Matters" will be very helpful to users of public toilets who may have concerns about their legal right to have single-sex toilet facilities. It should certainly help you to have a sensible conversation with any provider of such facilities. You can print a copy free-of-charge from this link:
sex-matters.org/posts/publications/toilets-matter-a-short-guide-to-law-and-good-practice/
Best wishes for your success
Susan, Mother of Invention