Good luck moogdroog - v good advice here.
I'd say, do make sure that you are aware of the NICE guidlines, which include the relative physical risks of a C section - they do need to make you aware of the physical risks otherwise they aren't doing their job, so it will help you if they can see you have made yourself aware.
That said, you are requesting a CS on psychological grounds. Standard patient info doesn't cover that, so you will need to be very clear that's your concern, and that given your previous birth experience and the mental health consequences for you, that is why you feel a CS is the right option for you this time.
I say that only because you don't really want to get trapped in a to and fro debate about theoretical physical risks (unless there is something in your personal circumstances that merits it) when you're actually requesting a CS on psychological grounds.
Also, if you get an unsympathetic consultant who keeps stressing how much easier an straightforward VB will be for you in terms of recovery, point out that they cannot guarantee that's what you will have, and you are not prepared to risk another traumatic labour.
Hope that makes sense. Just make sure too that as this is a 32 week appointment, and you are totally sure you want a CS confirmed, that they don't try to leave it up in the air until nearer your due date. There's no need for you to go through the stress of 2 odd months of anxiety and uncertainty when you would feel happier with a CS confirmed at this appt.
Just a personal thing - it's fine to be assertive, but as others have pointed out, you may not have a battle on your hands if you get a sympathetic consultant. You can go down the 'I want a CS and that's that' route if you want - but you can calmly state (or write down, if that's easier) your feelings about your last birth, and how traumatic you find the idea of attempting a VB.
I very much dislike like the idea that women have to go crying and begging for a CS to show how distressed they are (and extreme distress doesn't always manifest itself like that in any case). But if you think it might help, you can prepare a phrase or paragraphs beforehand to describe clearly how you feel so you aren't left floundering to describe painful experiences in the meeting.
Good luck.