Branwen,
Welcome to the site.
Dena has made some good suggestions and ideas.
I agree that kids tend to be better with the idea of the trans community than adults. I actually just came out to my younger two daughters this past week end and was amazed at how supportive they are. Perhaps more so than their mother and she is pretty impressive. I will admit, girls seem to be cooler with the idea(not sure if it is true but from my view).
I think that the therapist is the most important, biggest step. They can help you make your decisions and safely guide you. I think the biggest question at this point is how important is it to you to explore and maybe become the person you feel is inside. It is not an easy path. However, it can change your life.
Keep asking questions of yourself, to us and your eventual therapist. Just asking yourself can lead you to a very short path of nowhere.
I wish you love, acceptance and a smooth journey, wherever it takes you.
With warmth,
Joanna