After being on here for a while, I wanted to share my success story in the hope it could help someone else.
My 8 year old had been for all the normal tests, and nothing came up. Referred to a very unhelpful service for bladder training, who basically tried to do everything over the phone, apart from I only got to ring up to an answerphone and she expected that when I answered the return phone call that I could talk to her for half an hour! It wasn't working for us, so gave up with that.
So I was in the local library, not looking for it, but a book jumped out at me called "Stop Bedwetting in seven days" by Alicia Eaton. I thought, what have I got to lose? It basically uses NLP techniques to train the brain and the bladder muscles. We spent longer than 7 days doing the exercises before losing the pull-ups, but that didn't matter. You can adapt the method to suit you. There is also a website: stop-bed-wetting-in-7-days.com
We are currently on the ratio of 8 dry nights to 1 wet after one month in, which is fabulous progress. As I said, sharing in the hope that this method may help some other people.