BarrackerBarmer
Thank you for your advice, and I'll accept it with all best intentions 
I think the problem is (and this probably affects others with gender dysphoria too), a degree of body dysmorphia. The two seem to interlock.
I obviously support personal autonomy and everyone's self-determination over their own bodies. As I go through the medical process to ease (I won't use the word "cure) my gender dysphoria, making cosmetic alterations to bring my outward appearance in line with my sense of self is important.
Whilst I'm all too aware that the end-result will be "non-functioning", and some will see it as self-mutilation sanctioned by the medical profession - ultimately it will enable me to lead a happier existence.
I've not rushed into my transition, nor have I taken the decision to commit myself to such a "final" step lightly - but for "me", it's the right thing to do.
Essentially, and rather bluntly, it's just a cosmetic operation to make me feel better about myself. At the end of the day what I have underneath my jeans is nobody else's business other than mine and my partners. (Quick disclaimer that my partner of 6 years knew about my GD even before my first date because I told them). I'm certainly not going to go striding into a public place and go "LOOK AT THIS!" 
You're right though. I've thought and reasoned my way through all of this - and I'll never dismiss other people's advice/opinions. I've tried to accept my intact male body for over 20 years and I can't. It ain't gonna change anytime soon.
I'm proud to call myself trans/GNC. It's how I identify. I don't need to encroach upon/take away anyone elses rights to justify my own existence and place in the world.