You live in the Brighton area. This has probably skewed your perception of how this is perceived in the wider world.
Here are a few difficult issues that arise from allowing people to identify as the opposite to their own sex, which, let's not forget, was absolutely unknown as a concept until very recently:
Sport: most people can see that fairness is absolutely essential in sport. We have separate teams, competitions, records, medals and scholarships for female and male athletes so that the female athletes have some chance of winning and being recognised for their abilities. If they had to compete against male athletes, they would rarely even get into a team or squad, never mind win or break a record. This is because male puberty makes male bodies far more physically powerful than female bodies. Female bodies can do incredible things which male bodies can't do (pregnancy, childbirth, lactation), but because we have to develop and maintain a female reproductive system and for that we need female hormones (oestrogen, progesterone), we end up with smaller heart and lungs, less height, smaller hands and feet, less powerful muscles and wide hips, all of which means we can't run, jump, throw and hit things as powerfully as male athletes. Also, when it comes to contact sports it's physically unsafe for female athletes to compete with male athletes. One trans-identified male will potentially affect many, many female athletes, by putting some of them off altogether, by displacing others from getting a place on a team or a medal.
Prisons: more than 80% of violent crime is committed by males and almost all sexual crime is committed by males. Males with a trans identity retain a male pattern of offending, they don't have a low risk like females. This means that women in prison are very unlikely to be there for a violent offence and vanishingly unlikely to be there for a sexual offence. Research on women prisoners shows that most have experienced domestic and/or sexual abuse. Why should they be locked up with male offenders, who often are there for violent or sexual offences, because the male claims a female identity, in many cases only saying this after arrest?
Rape crisis services and refuges: here we have another group of women and girls who have been through traumatic experiences. Why should they be expected to share a safe space and confide their experiences with males? For many of them, it's known beyond any shadow of a doubt that that would compound the trauma, so a lot of them will just not seek help.
I could go on, but that's enough to start with.