“ Surely GCAUTIST if someone now advertises for a woman, then unless they add Transwoman, they must employ a biological woman?”
The specifics of this particular win are in relation to one particular scenario - sex representation on public boards, so yes if advertising for a woman board member for a public sector organisation according to this ruling it ought to be a female person getting the position. In regard to general employment, some statements have been made that can be used persuasively in future arguments but that will need to be tested and the private sector might find a different set of rules apply.
As for saying not providing single sex facilities is discrimination - that is situation specific too. There is no legislation or ruling that says you can force a counselling and victim support service to only provide a service for women. I was responding to the ERCC thing, not in general - it’s not discrimination to set up a service that may be used predominantly but not exclusively by biological women. It’s not discriminatory but it is in extremely poor taste imo, others seem to disagree. It is an internal policy decision. They do not have to apply the single sex exemption but it is highly questionable that they don’t given their remit.
If MW was given a job where they specifically stated a single sex exemption applied then it possibly could be challenged but in the end they can just change their employment policy. There may be funding implications I guess if they have been given money specifically for a woman to run womens services and that turns out not to be the case but that’s a different issue.