I don't know about hypnobirthing per se (as in the Mongan method), but I did natal hypnotherapy and you absolutely can learn it yourself and you don't have to practice for long if that's all you have. The CD was £12 and the book was about the same, which I think is a really reasonable price. And it's never too late to start if you can devote time every day to practicing. Natal hypnotherapy has a bunch of birth videos on their website and one of the mums only practiced 4 times before her birth and she is amazingly relaxed. I think it's worth a shot. I would just find something that is simple - one track to listen to, not some complicated study plan where you have to do so many things over several weeks for it to 'work'. NH is just one 40 minute or so track and that's it. You just listen to it as much as you can.