Hi
I haven't heard of anyone receiving a grant towards the cost of a family holiday, but certainly there are some organised holiday camps specifically organised for Type 1 children. Diabetes UK runs them every year and you can apply by referring via their website.
Also, you could ask your child's diabetes specialist nurse - as they usually know what is available. At our last clinic appointment, our nurse tried to 'sell' my son the idea of an activity holiday camp for teens in Scotland. I'm not sure which charity was funding it, because my son wasn't liking the idea and turned it down flat.
I do know many parents whose children have been on the DUK camps and their children have had a wonderful time and they have thoroughly recommended them. I think you need to apply quite early on for the coming year's holidays.