I did natal hypnotherapy from about 32 weeks (first baby). I chose that over hypnobirthing because they don't claim it'll give you a pain free labour (which I didn't feel was feasible for me). I wanted something that would give me a sense of control, no matter what happened but I went in with an open mind and ready to go up the pain relief scale as I needed. I think if you push yourself to have a pain free labour you could end up disappointed if you need drugs/epidural.
I'm an anaesthetist and have seen hundreds of births and honestly each one is different in terms of pain level, so please don't plan too much. My birth plan was healthy mum and baby please - anything required.
I started with pains at 40+11 and had stop start labour. At first just felt like period pains and used the hypnotherapy techniques; I honestly wondered why it didn't hurt more. Then it stopped for a few hours and then the following day I got proper contractions (and for me they were considerably different to period pains!) and used hypnotherapy plus TENS. Then stopped again that night for about 6 hours. Finally started properly at 40+13 at midday and progressed quickly, again using tens and hypnotherapy and paracetamol. Went to hospital 3 hours later by which time each contraction really hurt but I still felt in control and coping - I was 7cm on arrival and gratefully grabbed hard onto the gas and air. Had to have a CTG trace and not enough time to fill the pool for my planned water birth - pushing within an hour and delivered an hour after that. I didn't have any drugs other than gas and air but that's because it was all so quick, not because I'd have felt less good about the whole thing.
I used natal hypnotherapy, actively concentrating on it, until transition (shortly after arriving at hospital) but after this it was too intense to do picture the mental images required. However, the midwife commented on how calm I was throughout the whole thing and I certainly didn't lose it at any point. BUT - i gave birth within 3 hours of getting to hospital and I'm damn sure I'd not have been calm if it had gone on for hours and hours. In my opinion nothing helps with pushing the head out, you just have to grit your teeth and push beyond what you think you can bear, though the intense relief when the head's out is almost worth it and holding your baby is worth it twice over!
I've no doubt that natal hypnotherapy helped me:
Sleep well in late pregnancy
Relax in pregnancy
Cope emotionally with going very overdue
Control my pain in the stop start phase of my labour and up to going in to hospital.
Feel in control all the way through
Feel positive about my experience
I don't think it helped with giving me a straightforward birth - I was just lucky (but it's worth remembering that the majority of people do have normal births). And I doubt it's value in very late labour.
But since the CD costs about £12, I think it's value is indisputable and I wouldn't think of giving birth without it.
Soory for the long post, but it's what I would have wanted to know when I was chosing.
Good luck!