I get the gist that the GRA had the effect of avoiding certain human rights problems and, therefore, repealing it would conflict with our obligations under human rights law.
Some of the problems have already been solved, by the legalisation of single-sex marriage and by equalising tax and pensions law.
The other obligations laid on us by Goodwin are the legal recognition of transsexuals (GRA) and non-discrimination against them (EA), which seems unobjectionable.
The other implied outcome of Goodwin (transsexuals to be treated in law as if they had actually changed sex) has to my mind been effectively overturned by the EA itself.
Summary of relevant parts of Goodwin:
No concrete or substantial hardship or detriment to the public interest had been demonstrated as likely to flow from any change to the status of transgender people. Society might reasonably be expected to tolerate a certain inconvenience to enable individuals to live in dignity and worth in accordance with the gender/sex identity. It concluded that the fair balance that was inherent in the Convention now tilted decisively in favour of the applicant. There had, accordingly, been a failure to respect her right to private life in breach of Article 8.
I think it's fair to say that a substantial detriment to public interest (the rights of women and religious minorities) flows from treating transsexuals as having actually changed sex), and the EA solves this by treating the various protected characteristics involved completely independently of one another.
The sexes must by law be treated equally as far as possible, but when they really need to be treated differently then that cuts across other PCs and can't be overridden by a GRC.
I see a problem with Article 8 (right to privacy - part of Goodwin's case was that the fact that she kept the same National Insurance Number meant that her employer had been able to discover that she previously worked for them under another name and sex, resulting in embarrassment and humiliation).
The GRA has turned everyone's birth sex into private personal information. This must be reversed. Sex discrimination law is unworkable if we don't know people's sex.