Thanks for the comments chaps!
As for the flying, I've done enough to know I like it (7 1/2hrs gliders, approx. 6hrs powered - including 10mins at the controls of a Junglie Sea King!).
My present ACLO and his predecessor never mentioned the leadership course at HMS Collingwood, nor is there any mention of it on the RN web site. I think I'll phone the careers office and find out some more.
As for my debrief with the ACLO, I was told that I had done well in everything except the PLT (task completed in half the allotted time, but not enough presence by me as a leader - worked well as a group member though), and the competency based interview (not enough managerial/supervisory experience).
As for going back with more humility, I didn't go to the original board thinking I was God's gift - if anything, I was rather nervous (fear is healthy in small doses, I suppose). Sorry if I gave that impression.
Now, where to go on vacation......