Assuming it to be compliant with all relevant legislation (which is another discussion), which public services make more (or enough) sense to separate by self-defined gender rather than by sex?
We are often told that segregating by sex is permissible but not the only way to split "men" and "women" and that it's proportionate and appropriate to split men-identifiers from women-identifiers in some services in "appropriate circumstances" or some other phrase.
What are those services, and what are the appropriate circumstances?
This is a question about services, so I'm explicitly not referring to what the EA2010 covers under associations. Social groups are not services, and they can already be split or made exclusive in a much wider range of ways; I'm not asking about them. Only about public services. For clarity it's probably best to avoid terminology like "single sex spaces" because it's easy to misunderstand whether a "space" is a service - or an association.
So - which services can appropriately be segregated as women+trans-identifying men (women+ "trans women") and men+trans-identifying women (men + "trans men")?