//...a GRC allows a trans person to be married buried and registered as their preferred sex...//
"As their preferred gender", surely. Gender is a matter of opinion, biological sex is a matter of fact, determined at conception and is immutable.
//ed davey is correct and rishi sunak is wrong//
Depends on what you accept as fact. If you accept that a man who decides he will call himself a woman is genuinely a woman then Ed Davey is correct. Fine if you are happy accepting fiction as fact. If, on the other hand, you believe that a man who decides he will call himself a woman is simply that and nothing more, then Mr Sunak is correct. A man exercising his right to call himself a woman does not turn him into a woman, it simply demonstrates that he has a particular opinion that does not accord with the facts. Nothing wrong in that - politicians do it all the time.