https://www.thenorthernecho.co.uk/news/24628298.darlington-trans-nurses-set-new-union-amid-legal-action/
It looks like the Darlington nurses have set up or are setting up a new union - Darlington Nurses Union (DNU).
I can't find a direct link to it, but I guess it's early days.
Their new union, the Darlington Nurses Union (DNU), is believed to be the first of its kind taking a firm "gender critical" stance.
They have outlined their three founding principles:
1. Equality and respect for all workers regardless of their protected characteristics (including both gender reassignment and biological sex).
2. Securing and defending workers’ rights, dignity and decency at the workplace (including in particular access to safe single-sex areas for changing and hygiene, and protecting women from inappropriate exposure to members of the opposite biological sex).
3. The right to raise concerns about any genuine workplace issues without fear of retribution, and to have such concerns addressed promptly, constructively and reasonably.
There's also the Free Speech Union. They have successfully represented many gender critical women.