Mandatory Separate Provision (with exceptions):
Workplaces and some public buildings: Regulations (such as the Workplace (Health, Safety and Welfare) Regulations 1992 and new building rules as of July 2022) generally require separate toilet facilities for men and women.
Exceptions: Mixed-sex (unisex) facilities are permitted where each toilet is in a separate, fully lockable room, intended for use by one person at a time.
Transgender Access and Non-Discrimination:
Organisations can exclude a biological male (whether or not they identify as a woman) from women's single-sex toilets and vice versa.
However, trans people must not be left in a position where there are no facilities for them to use at all.
The recommended solution is to provide mixed-sex (universal) facilities in addition to the single-sex ones, where possible.
New Building Regulations: New public buildings are directed to prioritise single-sex toilets, with universal toilets provided only where space allows.
Guidance from the EHRC: The Equality and Human Rights Commission (EHRC) has issued interim and is preparing a full updated Code of Practice on the matter. The guidance states that allowing use based on gender identity invalidates single-sex provision.
No "Bathroom Law" for Individuals: There is no specific criminal law in the UK that prevents a person from using a particular toilet based on their sex. The law is focused on the provision of facilities by service providers and employers. If a property owner asks someone to leave their premises and they refuse, it could become a matter of trespass.
The ruling provides a clear legal framework for policies based on biological sex, but organisations are still navigating the practical implications and working to ensure compliance while also considering the needs and safety of all users.
(Sorry generated by AI and no time to find links for source)
I thought the older regulations (first in list) means that single sex as in biology had to be provided as well as other facilities such as disabled facilites and unisex.