This is from a while ago on this thread, but life got in the way of my mumsnetting and I didn't want it to go uncorrected:
he 2010 Equality Act and 'gender reassignment' characteristic that states in legal terms trans women are regarded as female, and trans men as male, as the default position.
This is not what the EA says at all. This is what s. 7 of the EA says:
(1) A person has the protected characteristic of gender reassignment if the person is proposing to undergo, is undergoing or has undergone a process (or part of a process) for the purpose of reassigning the person's sex by changing physiological or other attributes of sex.
(2) A reference to a transsexual person is a reference to a person who has the protected characteristic of gender reassignment.
(3) In relation to the protected characteristic of gender reassignment—
(a) a reference to a person who has a particular protected characteristic is a reference to a transsexual person;
(b) a reference to persons who share a protected characteristic is a reference to transsexual persons.
Section 11 is about the protected characteristic of sex:
In relation to the protected characteristic of sex—
(a) a reference to a person who has a particular protected characteristic is a reference to a man or to a woman;
(b) a reference to persons who share a protected characteristic is a reference to persons of the same sex.
Whilst a man could, of course, claim sex discrimination as a man, overwhelmingly it is, as we know, women who experience sex discrimination.
It is the GRA which (at section 9) states:
(1) Where a full gender recognition certificate is issued to a person, the person’s gender becomes for all purposes the acquired gender (so that, if the acquired gender is the male gender, the person’s sex becomes that of a man and, if it is the female gender, the person’s sex becomes that of a woman).
With a GRC legal sex is changed and a person with a GRC could, for example, use the EA to invoke the protected characteristic of sex and claim sex discrimination in relation to their "new" sex. So a transwoman with a GRC could claim sex discrimination as a woman.
Without a GRC a claim to sex discrimination would be in relation to their natal sex so a transwoman would have to show discrimination because s/he is a man. Any claim made due to their being trans would be under the protected characteristic of gender reassignment.
At the moment there is gatekeeping as to who gets to change their sex (or is it gender? the GRA is so badly written) in the shape of the "bureaucracy" required by the GRA. The EA is nothing to do with that.
If the gatekeeping/bureaucracy is changed so that it is much easier to get a GRC, many more transwomen will be able to claim the protected characteristic of sex as a woman.
(NB I haven't gone into the exceptions, I think you'll all have had enough of the legal essay by now).