Hi Lorna.
No, being on insulin doesn't necessarily make you T1. I am T2, and have been on insulin since diagnosis a couple of months ago (recently started taking Metformin too, and gradually reducing the insulin dose, to the point where the DN is making encouraging noises about stopping it altogether).
My understanding from the forum is that plenty of T2's take insulin as part of their treatment.
As I understand it, the difference between T1 & T2 (rather simplistically put) is that T1's do not produce their own insulin, while T2's do produce their own Insulin, but the body is unable to use it efficiently...
I am sure that many more experienced members will correct me if I've got any of that wrong!
Still a bit new to this game, but have learnt SO much already from this forum and the support and information is fabulous!