Obviously the OP is just on a wind-up, but this is an important topic that deserves to be discussed.
Medical litigation is really hard, for two reasons. One is the three-year time limit, which means that a lot of people who experience negligence never take legal action because in those three years they're still coming to terms with what's happened. For de-transitioners, who might not regret their decision till four or five years afterwards, it's completely hopeless.
The other is that the bar for proving negligence is very high. You have to prove that the doctor caused you harm through negligence, by doing something that a reasonable doctor wouldn't have done. (That isn't the exact wording, but you get the idea.) But the problem with the trans medicine stuff is that it's not like, say, a botched operation where you amputate the wrong leg.
Suppose the doctor has performed a double mastectomy on a healthy 19 year old woman who is gender dysphoric. The mastectomy might have been performed expertly with no more than the expected side effects. The problem here is not the incompetence of the individual doctor but the question of why the hell the NHS is performing double mastectomies on physically healthy but mentally unwell young women in the first place. And that's not a question you can resolve through litigation - you really need something else like judicial review.
So I think it could be a while before we see a successful medical negligence case in gender medicine. I hope I'm wrong.