I'm a teacher in a school in SE that has this new layout and to be honest I have not heard many complaints from girls. I have had a few issues from girls wanting fix their hijab and not finding a space to do so but even they have found ways around it, although not really ideal for them I admit.
It is widely open and there are staff monitoring the corridor during break and lunches, from my experience as I was on duty in those areas. Credit to the kids they do just walk in and out and boys wash their hands because they are seen and can see the teacher hovering around. Also, the fact that it is so open actually has helped behaviour. It has also meant the area is typically cleaner than say, boys toilets. So overall standards are higher.
I hated the idea at the beginning but it hasn't created many problems. What I don't like, which is what we also have in the building is a unisex toilet space where the main doors are closed; a few cubicles, and shared washing space- I can't know what is happening in there. Those are for 6th formers.