From what I've heard, the process is likely to include a statutory declaration where you commit to "live as" your declared gender permanently
and apparently possible penalties if you don't
The stat declaration was to a solicitor (I think that was meant to impress on us just how legal they were being) but people lie to solicitors all the time, so it's a non starter. Solicitors are not police and dont much care if you break a declaration, nor would they know if you broke it.
Also, in the Scottish proposal (and I imagine in any coming English proposal) there's some sort of waiting period before you'd get the certificate and therefore also a wait before you could change back
The point of self id is to immediately change gender once you figure out which of the 311 you are, Scotland has recently changed its definition of woman, this definition doesn't include adult human female.
And this change back gender is a bit peculiar, there are 311 genders, surely one of them would fit better than "just" male or female ?
Also ask pips bunce what gender they are on a different day, also please ask about gender on passport/DL, and also while your at it ask pips why they veer from masculinity to femme and not try one of the other genders ta.