There’s never going to be a perfect solution but what we had was based on health, safety and welfare. Public toilets are even specifically mentioned in clause 71 of the Sexual Offences Act (2003) and implied in voyeurism laws.
If you look at the Government’s Provision of Public Toilets (2008) (it’s googlible) you can see these are what are being discussed. There is nothing about men using womens toilets or vice versa. There is lots about men’s behaviour in toilets and women’s needs. Vandalism, sex, drugs, queues, problems with disabled toilets and misuse, lack of safe facilities for women, are all in there.
What has changed since 2008 is the loss of council public toilets so people are using venue toilets which have used a variety of rise of designs (seemingly building control is not used), mobile phones and transactivism: the rise of the unregulated and ill defined gender-neutral or ‘inclusive’ toilet. Now we have the rise of cheap hidden cameras, the easiest places to hide them and one where you are not noticed setting them up and one where they can be hidden easily amongst mechanical ventilation etc.
Voyeurism with mobile phones is a boy/man problem. But the way to prevent that it not to reduce health and safety by making designs completely private.
Having sex in toilets is illegal but the way to not have to deal with it in pubs and clubs is not to enclose toilets, because you have to consider unconsensual sex as well. Similar reasons with drug taking and overdoses.
The ‘out of sight, out of mind’ approach is not safeguarding.
Because most of the toilet behaviour is so sexed, the best way to deal with it is to have single sex toilets as the primary provision with healthier and safer non-enclosed designs. This prevents misuse, is better hygienically and most importantly protects anyone who is in need of help as they will be seen quicker and heard if they are able to make a noise, as the designs for single sex toilets can then have gaps in the doors and partitions. The ability for women to say ‘No’ and know that the government is behind you and you are not going to be prosecuted for harassment (or lose your job), which has been implied by others, is the thing that needs to be sorted out.