Universities are a weird one. They are under the DfE but don’t have the DfE design guidelines of further education and schools .
I would say in many schools, visitors (parents, community groups) are encouraged and they use the school toilets. Where you go on parents’ evenings for example. Schools were encouraged to invite groups in for extra revenue. That’s when I think the 1992 gets a bit blurry as some of these will be adult groups for example, paying a skills provider who pays the school. Only the staff toilets are covered by 1992 otherwise, that’s partly why we have such mad secondary school designs.
The other thing that came before 1992 is, of course, 1974. Which briefly discusses toilets but does say that you have to regard visitors to your premises. The Health and Safety at Work etc Act 1974 is the primary piece of legislation covering occupational health and safety in Great Britain and what 1992 had as a base. Everyone has to abide by that one.
Presumably any visiting staff using changing rooms in hospitals or visitors using toilets would have to be asked if they minded the single sex being mixed sex?
https://www.hse.gov.uk/simple-health-safety/workplace-facilities/health-safety.htm
The HSE says reasonable adjustment for a man with prostate cancer is to have a bin in the men’s. It says you must have suitable toilets for disabled people. I believe a reasonable adjustment for those with conditions where they could collapse, which includes workers and visitors with epilepsy, heart conditions, diabetes etc, is a door gap at the bottom of the door for safety. This is not ‘just’ about putting a sanitary item in a bin, this is actually about safety. I feel so strongly about this after researching the tragic preventable deaths in public toilets, that would take it back to Article 2: www.equalityhumanrights.com/human-rights/human-rights-act/article-2-right-life
Enclosing all the toilets hasn’t been an issue in workplaces with traditional mens and women’s. If it all goes enclosed, then there’s no safe loos. I have no accounts of people with collapsible conditions managing to pull an alarm beforehand, which of course there isn’t anyway in normal loos. I have no accounts that women and children being assaulted in enclosed toilets managed to pull an alarm beforehand. I expect in the latter case in could have been dangerous to do so.