The granting of a GRC should give people the Protected Category of Gender Reassignment under the EA, that even if a GRC were now given on a self-ID basis, that would be fine. Then they will be protected from discrimination due to their gender reassignment.
What needs to be urgently changed is the amending of the sex marker on a birth certificate. There is no jusification for that.
Allowing a change of a sex marker conflates two separate categories, and has now left us in a position where there is no longer a single record anywhere of a person's actual SEX. Therefore, no way of ever "proving" legally who is a transwoman and who is a woman.