Hi Rugbygirl,
Just joined this forum and saw your post. Not sure if you have found all the answers you're looking for but maybe I can share a little of my experience.
I am a type 1 and just started cycling again after not being on my bike for a year and a half.
Fuelling for me seems not to be so much different than for "normal" cyclists. I try to stick to an energy bar each half hour till 45 minutes and use an electrolyte drink and an energy drink aiming around 500 ml each half hour. Not with to much carbs/sugars. The sachets mostly recommend 50 grams of the powder on 500 ml water but I normally use around 35 to 40 grams on 750 ml. I find that I mostly don't have to use any insuline or very little while cycling and eating the bars and drinking but I don't know how other T1's experience this.
I do not race but mostly go out on my own and every now and then I join an event. I try to have a pit stop in the middle of my ride and do a bloodsugar test and depending on the result I eat some extra. Certain gels are very helpful too but there are quite a few which contain a serious amount of sugar. There are some brands which are really good and taste good too but this is something which is also a very personal thing which any cyclist will agree.
Good luck!