Sorry I haven't read the replies to your thread but wanted to add my two cents..
The thing is, you can refuse to consent to medical treatment, and there are lots of reasons to objectively not want an assisted birth.
However, the circumstances in which they suggest assistance will not be without good reason to do so, generally speaking.
At the same time, some doctors and especially consultants are quite trigger happy as their priority is safe healthy baby, always. With my second child I was nearly rushed off for a c section. It was completely unnecessary, but they did not want to leave it up to chance at all. Baby turned out to he born about 15 minutes later and everything was absolutely fine.
So I would really push for informed consent, but again in the apex of labour it can be very difficult to weigh up your options logically. I was nearly given assistance to deliver my first, as I was at the end of my strength, and despite also being very very against assisted births I would have done anything at that point to have it over with.
There are just so many factors at play when it comes to birth. Your body, your baby, how you labour, yot midwife, your doctors, every combination can result in different scenarios playing out.
I'd say the best way to try and manage the situation is to make your preferences known, discuss them with you midwife on multiple occasions, discuss them in early labour if possible, and most of all, do everything in your power you can to avoid an assisted birth. So follow all the advice like active labour, date eating, staying hydrated, everything you can.
Hopefully you will not need an assisted birth, but I wouldn't let it become the focus of your pregnancy and labour. Best of luck :)