PercyIngle, you poor thing, this all sounds very traumatic for you.
I hope that Marie stopes will be able to help you talk through things in a way which makes it all clearer in your mind.
Of course you know now that there are two very separate issues - whether you would terminate to avoid risking the horrific birth experiecne (including your PND difficulties), and whether you wnat to be pregnant / have a child per se.
If you are confident that you simply do not want another baby - that is your decision, and I can tell you from my own experience that termination when you fell sure that you do not want to be pregnant, and have no personal barriers to early termination, can be a straightforward experience, with no lasting feelings of regret or guilt. OTH I think that if you would, in your heart of hearts, like another baby but can';t face the process, then you would risk longer term problems. In any case, it may be helpful for you to get more help in dealing with your terrible memories of what happened.
In the end, would you be
a) simply relieved not to be going ahead and having another baby,
b) feeling 'I wish I could feel happy enough about childbirth to have another baby?
Or - would you be thinking of a termination even if your last birth experience had been happy?
If not - there are all sorts of sources of help and support. Counselling of the post-traumatic-stress kind, working with a doula, attaching yourself to a midwife service that sees the same patient throughout - the brierly practice in S London, fofr e.g, attached to kings, and NHS, specialise in working with women who have mental health / depression problems (and your PND would qualify you).
But if, in the end, you simply don't want another baby, then the birth problems are not especially relevant to your decision making, perhaps.
Good luck.
You have a right to feel all you are feeling - don't clamp down your thinking with guilt and self-duobt.