They're good, but I think we also need some that makes sense to people who are not aware of the issues. Before I joined Mumsnet, these stickers wouldn't have made any sense to me and I have been an active feminist for a number of years. And I know lots of lesbians and transexuals.
I would suggest the following:
KEEP MALE PRIVILEGE OUT OF OUR BATHROOMS
Did you know that proposed changes to the law mean that ANY man could use the Ladies toilet simply by saying he identifies as a woman? This doesn't just cover transexuals but ANY straight man with a penis.
In the last 5 years there have been [data] attacks worldwide by men identifying as woman in female-only spaces, including prisons, domestic violence shelters, etc.
We need to protect ourselves, our daughters, our mothers, our sisters and other women. Please helpt to STOP this Act becoming LAW.
[Call to Action].
Sorry, it's just a draft, but I was trying to come up with something that you could read during the time it takes to have a wee. An A5 sticker on the back of every toilet door would spread the word and educate people to what is going on.