I'm pretty sure I can legally complain about my college's toilet provision

[Capillaryaction]

Hi, I've started work in a new college (new to me).
There are separate blocks on several sites.
One new block with eight classrooms has
one toilet area with 12 toilet cubicles.
These are ALL designated as gender neutral, with a sign up saying 'these four have sanitary facilities'.
This block is used by equal amounts of boys and girls.

I'm pretty sure they HAVE to designate some as exclusively for women?

It depends whether they are fully enclosed with individual sinks in each cubicle.

No they are not enclosed with a sink.

I think there is detailed info about legal requirements on the Sex Matters website.

Ok great.....toddling off to check

Is this a 16-18 college or are there under-18s studying there (even if it's not mainly for that age group)? In that case, you are going to be under the Schools regulation.
As lecturers might also use the facilities, you'll also be under Workplace regulations, unless there's a separate set of staff sex-segregated loos.

So you could have a situation where a lass could have to let someone go ahead of her in the queue because she needed one with sanitary provision ? And they think that’s ok? To announce to the world you are ok your period ???

and then if the lass leaks she has to clean up in a mixed sex area - they think that’s ok?

I would be furious

There are no staff toilets. I have trouble with my bowel ATM (being investigated).
I can't imagine having to use it and my rough and ready male students using the cubicle after me. I'm upset about it.

If you are in a school with minors they must provide student only toilets (single sex blocks or fully enclosed single occupancy units) unless it is an accessable (disability) unit.

https://www.legislation.gov.uk/uksi/2012/1943/regulation/4/made

Toilet and washing facilities
4.—(1) Subject to paragraph (3), suitable toilet and washing facilities must be provided for the sole use of pupils.
(2) Separate toilet facilities for boys and girls aged 8 years or over must be provided except where the toilet facility is provided in a room that can be secured from the inside and that is intended for use by one pupil at a time.
(3) Where separate facilities are provided under paragraph (1) for pupils who are disabled, they may also be used by other pupils, teachers and others employed at the school, and visitors, whether or not they are disabled.
(4) Suitable changing accommodation and showers must be provided for pupils aged 11 years or over at the start of the school year who receive physical education.

If all the units are blocks that students can access the employer has no lawful employee provision

If you are accessing a semi-private space where you can be alone with a student you are at risk under safeguarding.

If you are in a union I would be asking for support in that as no adult should have their reputation or even freedom put at risk by being forced to enter what should be student toilets.