Tommo, like yourself I was knocked back when I first applied to join the UAS. At the time I thought it was the end of any hope I had of flying fast jets, but I was wrong. As has been mentioned, you would be amazed how many people were rejected on their first go.
I would echo the advice given above, a polite letter to the UAS squadron commander asking for advice on how to improve your application for the next year would seem sensible. If it's worded anything like as well as your post, then you should do fine.
Don't give up - you stand every chance of success next time around. Best of luck.
Blunty