That would be interesting.
How does someone responsible for safety on sight behave if they see 5 blokes, including some with facial hair, entering the toilets?
If they DON'T remove them and something happens their jobs are on the line.
If they DO remove them and a complaint is then made, their jobs are on the line.
They don't actually have much legal protection because these venues don't have an adequate policy over single sex provision / anti sexual offenses because so many of these venues are refusing to define what a woman is.
It leaves staff in a position where they have to make a judgement call without the support of their employer upfront.
What are supposed to do?
If can't assume anyone is a man, so they can't challenge anyone who looks male. That means they can't necessarily do their job.
This is where the 'reasonableness' test should be relevant. Is it reasonable to challenge, and if necessary remove, a group of people who you perceive to be male who are congregated in the female toilet if you are security guard tasked with ensuring safety of all guests and not automatically fear losing your job?
If the answer to this question is 'no', then we have all sorts of further questions.