Hi there Sarah, my 18 yo daughter belongs to the Facebook group, Type One Teens. It was set up by the daughter, Georgia, of the admin of a couple of parents groups I belong to. It's quite an active little community - no parents allowed! Also, Diabetes UK do some fantastic care events for teens - Centre Parc weeks for example which are a great place to meet others in your situation. Keep an eye out here as new dates for 2017 will be announced in the next month or so: https://www.diabetes.org.uk/How_we_help/care-events/Young-People-Events-11-17-years/
You also might like to become a JDRF Youth Ambassador and once again you will get the chance to meet others. https://jdrf.org.uk/get-involved/volunteer/be-a-t1-youth-ambassador/
You're probably overwhelmed with your new diagnosis but there's no better people to see it from your point of view than other teens!