The only experience I can recall is that my sister was a hypnotherapist and used to help people overcome problems with smoking, nerves before interviews, nerves before driving tests, and exam anxiety etc, and she had some success.
As far as aaaaaaaaaMarple hynotherapy is concerned, I know the chap personally and he seems a decent chap, while I don`t wish to advertise for him, if you give the centre a call you may learn more - maybe to your liking, maybe not.