I have realised I am very confused. I wanted a separation between "genuine" trans women and those ne'er do well's seeking access to women's spaces for nefarious reasons. I have no problem with the first group and serious problems with the second. It turns out there is a separation - the gender recognition certificate. What is so bad about the GRC? (Apologies if I being ignorant.)
Because this certificate is issued to males who do not have surgery (and some people on here have been complaining about such a condition "forcing" males to have surgery) and whoever gives out the certificate is at as much risk at being told utter bullshit and believing it as the general population. Because "gender" is nothing provable. You would probably have better success trying to find out who is a genuine Christian by doing brainscans!
Of course, a male who had his penis and testicles removed is still not female, but he could not commit rape (according to UK law) and if he committed sexual assault one can hope people would be a bit more ready to believe the victim that she did not want a random object inserted into her vagina than people are after a rape with a penis.
A male who had his penis and testicles removed would also not be able to show his penis to girls in the women's changing rooms at a pool.
So, all in all, surgery as a condition to being recognized as female by the law (except in sports, because male muscle and bone structure is male muscle and bone structure, no surgery can change that) would be somewhat tolerable.
GRC is just a requirement for a male to have worn dresses and makeup for a while, or whatever the person deciding thinks "transitioning" means - it explicitly does not require surgery.
Male sex offenders are happy to wear dresses to get access to vulnerable women. Some even especially enjoy it, but I do not doubt that even some of those who do not would do it to get access to vulnerable women - especially those who are in prison and have nothing to lose and everything to gain.
Changing that to every male getting to decide for himself whether he feels like a woman that day makes things worse, of course. But GRC is not much better.
I focus on males here, because only the very rare FtT who is still a teenager and does not know how the real world works would ever be as stupid as to want access to men's changing rooms and toilets, let alone men's prisons and mental health wards.
There are some FtT who are really surprised men rape them, by penetrating their vaginas, without asking what their gender identity is. But those are rare.
Most female humans know that male humans like to rape us, and that any genderfeelz WE have or claim to have, will not stop them from doing so.
FtT only want to use the men's bathrooms if they pass as male, and can be sure to be treated as male, i.e. not sexually assaulted or raped by males outside prison. They need no extra laws for that. (And since males regularly rape other males in prison, I am sure no significant number of FtT wants to be imprisoned in men's prisons)