I've got a few thoughts on it.
Firstly, I think you need to make it snappier, and less based on a few anecdotes. Use the anecdotes, fine, but back them up with research about the interventions rate, statistics of tearing etc, to show that you aren't just taking a few isolated incidents out of context.
Remember that the more detail you go into, in some ways, the more they have to come back on.
Secondly, some of your concerns like pph are actually a higher risk with a section, so I'm concerned that your are shooting yourself in the foot.
The things you need to mention that scare you are those that are typical/risks with a vaginal birth, but not so much with a section.
Thirdly, you mention your anxiety towards vaginal birth, but maybe more about the effect this is having on you. It's it causing sleepless nights, tearyness etc? Also mention that the unwillingness to discuss a section yet is adding to this stress, and the effect of this on you.
Fourthly, don't be afraid to quote the guidelines. You can do it gently. You could say something like you are aware the Nice guidance allows me the option for a section on request, but am concerned at the unwillingness to confirm so far, that I will be able to opt for a section, and that for your own well being and mental health, you need confirmation of this as soon as possible, so that you can start to enjoy the pregnancy without the fear of birth clouding everything.
Lastly (and this comes back to the guidance again), it is, (or should be at least) your decision how you give birth, not theirs, so don't delegate this decision to them in the last line. You aren't asking a favour, you are asking for something the guidance says they should give you. Don't go in all guns blazing at this rate, but if they are not following the guidance, then they should refer you to a hospital that does.
So I'd replace the last line with something like -
Thank you for taking the time to read this letter, and hope we can discuss the way forward together, as soon as possible, as the uncertainty over the birth is really affecting me.
Or somethibg. But don't give them the power to decide. It's your body.