I'm going to try to answer my own question here. I've just been reading the concluding parts of the Haldane judgement. She states, quite categorically:
"For all of the foregoing reasons, I conclude that in this context, which is the meaning of sex for the purposes of the 2010 Act, “sex” is not limited to biological or birth sex, but includes those in possession of a GRC obtained in accordance with the 2004 Act stating their acquired gender, and thus their sex. Such a conclusion does not offend against, or give rise to any conflict with, legislation where it is clear that “sex”means biological sex."
Nowhere does she mention the Equality Act's single-sex exemptions. She does mention other legislation that specifies that a service can be for biological females only, such as the Forensic Medical Services (Victims of Sexual Offences) 32 (Scotland) Act 2021.
As far as I can see, the Haldane judgement means that "sex" as used in the Equality Act refers both to biological sex and opposite-sex people who have a GRC, effectively losing single-sex protections for women. Am I wrong?