@Jonman . I do the gym 5/6 days a week and have done since and before diagnosis a long time ago.
Don't let your T1 stop you doing anything.
Respect it's power, by that I mean with regards to exercise it can lead to big changes in BS levels during and after exercise.
It'll be trial and error for you. Keep a record of what type of exercise you do and how it affects your BS levels.
Cardio makes me drop during and shortly after . Heavy weights make my BS rise during but then drop up to 6 hrs later.
You'll need to record as much as possible. Check your BS prior to a workout, if needs be check during and check after. This should give you a picture of what exercise does what to you as an individual.
Most importantly is to keep some fast acting carbs on you at all times, whether it be liquid or solids. Orange juice, Glucotabs or something similar. You may find you will drop fairly quick during exercise and you don't want to be caught out.
If you have a training partner, tell them how to spot and help you if your sugars go low.
It all sounds a bit daunting but honestly it'll all come together, your confidence will grow and exercise will be just as good as it was prior to diagnosis.
Good luck. If you need any more advice just ask there's lots on the forum who do lots of varied and extreme exercise regimes.
@helensaramay beat me to it