@mightbeasillyquestion I work in an FE college and I think a lot of students and staff would have concerns about this. I would start by raising it with your tutor if you have one - anyone who is assigned to you as a learning support. Ask them what the best way to make a complaint about this is. If you have a lecturer you trust and get along with, ask for their advice also.
Colleges tend to take complaints quite seriously when they come from students, especially if you are willing to keep pushing on it. Is there a student association or student union at your college? They might help (but they might not - approach with caution!) It would be a good idea to talk to other students so that you have some back up.
Really what they've done here is limit women's ability to access education. If you want to go to college, you have to share loos with males. That is going to put a lot of women off.
Have they considered the needs of muslim students? They will not be able to access the college if there are no single sex facilities.
I don't know about you, but in my college there are many students with mental health problems, and lots of male students who have criminal convictions and anti-social behaviour. It's not fair or appropriate for females to have to share in those circumstances (or any circumstances, imo).
The college probably also has a percentage of students with additional needs, who are particularly vulnerable. What is being done to safeguard them?
It's also very strange if they expect female staff to share with male students, and vice versa. There are many, many safeguarding concerns here.