trans is a PROTECTED LEGAL STATUS in the UK
The confusion over this is down to people wrongly thinking (and gender activists wrongly claiming) that the protections and rights afforded on the basis of "gender reassignment" are about trans people having a right to be treated as/given the right of the opposite sex.
They are not about that. No one has a right to access spaces, services etc. of a category they don't belong to. If you are male, you don't have a right to stuff that's for females just because you identify as or claim to be female. If you're male, you cannot be female. Just as if you are not disabled you don't have a right to a disabled parking space or to be in the paralympics, and if you are white you don't have a right to a scholarship or award that is for black people, and if you're 25 you cannot get your pension by announcing you're 70.
The rights and protections you do get under "gender reassignment" are the same as what everyone else gets, e.g. you shouldn't be discriminated against when it comes to getting a council house or a promotion etc. on the basis of being trans.
However, discrimination is legal in some circumstances on the basis of things like sex, disability, age, belief etc, when they are relevant. So for example if you are male you can be excluded from a service, group or space that is female-only. There are groups, awards and services that are for trans people and you can understand that they exclude people who aren't in that category, right? Then you can understand that other protected characteristics, like being female, can have the same.
If protected status for gender reassignment gave you the right to claim the rights of the opposite sex, which a human cannot be, that would in itself be discrimination because it would be discriminating against people who want to claim an age, disability, ethnicity etc that they do not have. We don't allow that so why should it be allowed with sex?