What it boils down to is that there are some male people who are very very upset at the idea of not being able to access female single-sex spaces. Jolyon has raised half a million quid on the promise that he will somehow persuade the legal system to fix it so they won't be upset.
Of course, if male people who would like to be female aren't comfortable using male facilities, they can always find unisex facilities. But we've been told repeatedly that this won't do, and it's very very important that there are facilities advertised as for female people only, which these male people get to access.
I hate to be cynical, but you start to suspect that access to unconsenting women and girls is the whole point.
And, because we can tell someone's sex by sight with almost total accuracy, but we can't tell someone's philosophical belief by sight, we can't restrict female spaces to females plus [males with a sincere philosophical belief that they were meant to be female]. If you allow some males in, then any male, with any agenda, can come in.
Or we can simply keep all males out, because female safety, privacy and dignity outweigh a small number of male people being sad.