Hi there 
Firstly, I'm so sorry to hear about the abuse inflicted on you and how that is affecting you now. Certainly, there should be scope for offering you an elective caesarean on mental health grounds.
In terms of the practicalities: If what you're asking is "can I tell them I know the risks and I've made up my mind?", the answer is - not really. This isn't out of cruelty, but a combination of factors. One is admittedly that, as things stand, the NHS isn't really set up to offer elective CS on request on such a casual basis (I realise it isn't casual to you, it's very serious - what I mean is, on such an instant basis).
But also (and, mostly) a natural birth is something that just happens (albeit it's advisable to have professional support through it), whereas a CS is something someone else does to you. Doctors are not technicians; just performing elective caesareans is about the easiest thing an obstetrician does. Assessing you to decide, along with you, whether it's in your best interest, is more difficult, and takes time.
It's true that it is a little later in the day than this issue is normally raised, and the usual process might have to be fast-forwarded in your case. It isn't "people trying to persuade you not to" (although I see how it might come across like that), it's people being sure in their own minds that you've considered all ways of looking at it, because ultimately they're going to perform a major operation on you, and they need to know it's warranted.
It does sound like you might be someone who falls into this fairly rare category, but you need to speak to a consultant ASAP.