Fairenuf no, I didn’t say anything even close to that.
Captain I am sure there will be a bureaucratic , legally binding process for self ID as there is for a variety of other this, e.g. registering a birth, getting married, changing your name. The UK does not have ID cards at present so you won’t be able to demand proof of someone claim but I am not sure why that is relevant. I have Greek ID card which proves my name, date of birth, address, etc, the UK seems to manage without, but if you think it would be better to have them fine.
Personally I am all for unisex toilets and changing rooms with individual cubicles. Changing rooms are frequently unisex in France and that in itself does not seem to raise rates of sexual assaults, rapes, voyeurism, etc.
Of course the underprosecution of sexual crimes is a huge issue, I am just not sure why you think trans women should be penalized for this!