Ok, Mat, even if it has nothing to do with the composing, still pretty cool!
That is, do you have an absolute ear? That's great. I can write down the score from hearing too, but I would always need a keyboard for it, because I am not sure whether I made a mistake or not. Which means, I can correctly identify the chord progressions, intervals etc., but I can never exactly say, what key is this.
Cool if you can - it actually means, you are able to write down a score, sitting in a train or on a beach - all you need for it is a pen and a sheet of paper. Right?