I'm not in the UK so will leave the local support group info to the others.
But if it's any consolation, there are shedloads of folks on this forum, and all over the internet, diagnosed as children or young adults and living long, healthy lives. Medical advances are such that diabetes really doesn't affect lifespan anymore, not in any meaningful way. It does change the life of the diabetic and of the family, sometimes in very profound ways, but at the same time it doesn't change anything. You can still go to school, hold a job, get married, have a family. There are diabetic Olympic atheletes, diabetic Everest climbers, diabetc Miss Americas! About the only things we can't do are drive some heavy vehicles and fly commercial jets. And that's because we're not allowed to, not because we're not able to!
I was diagnosed at age 10, now 28. Married for 8 years, moved to a different country, learned a new language, now taking a BA in that language, and will soon be undertaking a master's degree. We've got several members on here that have been diabetic for 30 years, 40 years, and more. How long has Richard157 been diagnosed? 60 years, isn't it? We also have a few members who are parents of diabetic children, hopefully you'll get a chance to talk with some of them. I know there are entire forums for parents/children also.
It's very hard at the beginning, very heavy and overwhelming. And it's more so with little ones who can't always tell you how they feel or whether something needs to be done. It does get easier, I promise! You're doing a great thing looking for others who are in the same situation as you. No one understands diabetes like other diabetics (or parenting a diabetic like other parents of diabetics). I spent many years in "diabetic isolation", and when I found this forum it was a godsend. So do seek out other people, it helps you have a better idea what's normal in the real world (as opposed to in the doctor's office - there can be a big difference sometimes) and thus helps you feel a little more sane. In addition to being a good source of information.
If there's anything we can help with, any questions you have, no matter how small, please do let us know.