"As a service provider, in most practical situations, it is not appropriate to treat a person without a GRC differently from one with a GRC."
And in fact you're not allowed to ask.
The law is firmly on the side of allowing giant beardy dave (and possibly his mates if they're out on the piss for eg) going into any and all women / girl only faciltiies.
And there's nothing anyone can do about it unless / until they actually attack someone. There are no laws against being creepy as fuck, wandering around naked in a communal changing area, standing way too close to poeple, followign them, saying odd stuff to them, staring, and the million other things creepy men do to upset / intimidate / scare women that are just this side of the law.
So there we have it. All of this - is in black and white in government guidance. Men must allowed to be able to do whatever they want. Women and girls must not challenge them, or expect any support from service prviders. If they don't like it, they can go somewhere else (or stay at home).
The conflicts with other protected characteristics are apparently irrelevant (religion for eg).
Which is what the girl guides said. In a conflict between teh rigth of religious girls to attend, adn transgirls, we choose the transgirls, teh religious girls should leave.