vesuvia and Kidnapped nailed it.
The 'trans issue' is not 'single issue' at all, but will affect pretty much all facets of life for the female born, maybe not all at once, but it is happening bit by bit. And the technique is 'thin edge of the wedge'.
Even just a few years ago, TIMs (unless they 'passed' really well, most don't) needed to have their Gender Recognition Certificate in order to enter female-only spaces like toilets (but more importantly, changing rooms). Now what is on the table is 'self identification' to enter those spaces, unchallenged (because if you do challenge them, you can be charged with a hate crime, and be labelled a 'transphobic bigot'). And that is why various groups of feminists are meeting to discuss the implications of the changes to the GRA, specifically 'self identification', because it opens up a range of issues for women and girls.
Women's refuges - will be forced to take in (and house with women) anyone who 'identifies' as a woman in the refuges. Of course, this can have life threatening issues for DV victims (and staff) if the abuser of a woman finds out what refuge she is in.
Women's prisons - most women in prison are in there for minor and non-violent crime (the majority with sentences of less than six months). Many TIMs (specifically the ones convicted as males) who later decide they are 'really women inside' have sexual or murder offences against women and girls. Ian Huntley.
Women's health - some quite delusional TIMs are lining up for 'pap smears', even though they have no cervix, taking resources away from women's health. Also, women who have a preference for female medical staff (esp for gynae matters) will not be able to refuse treatment from a TIM, because the female patient will then be deemed a 'transphobic bigot' for her preference. Actually, for Muslim women, this is not even a 'preference', they need to be able to see actual female medical staff (as well as, they would not be able to access women's refuges either, if unrelated males were housed there).
Women's changing rooms - a couple of cases in the US in the last few years illustrate this. One was a high school girls' swim team, whereby the girls & parents objected to the TW in the female changing room. The 'solution' was that the swim team were relocated to use a small utility room to change, and the TW continued to use the female changing room. In the other case, a woman at a fitness centre objected to a male (TW) being in the female changing room. She was advised that "she" (the TW) was allowed to be there because "she" 'identified as a woman'. The gym cancelled the woman's membership. She is currently suing them.
Sex equality in the workplace - places (like Labour's all-women short lists) are being taken by TIMs. The women who object to this, get booted out of the party. Equality monitoring in workplaces can now show a sudden increase in the number of women holding senior positions or equal pay status, even though many of these 'women' built their careers as men.
Crime statistics - Once upon a time, female sex offenders were less than 1-2% of all sex offenders (and many of those were accomplices). Now we have a sudden influx of 'female sex offenders'. Again, if Huntley gets his way, his crimes will in the future be counted as a 'female sex offender'.
Women's political/feminist organising - this has been under attack for many years now, half a decade already. Women are being hounded for even discussing changes to the GRA. How dare women have an opinion on something that might affect them!
This is not even necessarily a full list of implications, but the above is a wide sample of the areas that are impacted for women and girls. I have not even covered GNC (gender non conforming) children, and the future lesbian and gay kids who will be fast-tracked as 'trans', sterilised, and tied to the medical profession for the rest of their lives. Or 'the cotton ceiling', which insists that lesbians have sex with people with penises if they call themselves lesbians.
Transgenderism is far more than a single issue.