I'm in a staunch Labour constituency. My vote for another party, down all the years, has counted for nothing, not even close. Still, I've turned up t vote each election.
But now, the other party that I usually vote for, has come out in favour of gender self-id.
So it's a spoiled ballot for me this time.
I like other spoilers' suggestion of writing what you want to say, on a sticky label beforehand, to simply stick on your ballot paper, rather than having to scribble it all down in the voting booth!
A very good idea, and I shall consider my wording over the next few days. Probably along the lines of "Women don't have penises" and "Women's rights matter. Women = Adult Human Females" and "men are not women, men can never be women", or something similar.