Thanks for sharing, and sorry to hear the news. Did they tell you when you can apply again? It seems to be the norm nowadays... Anyway, keep your chin up mate, you will get it next time!
I guess it is important to read up on SPECIFIC parts of the aircraft that you will declare as your favourite. There is no way you will ever know as much as the interviewer, but if you are an expert in 777 fuel systems or the FBW system (as opposed to a little bit of everything on the aircraft), it could be a bonus if you can rant on and on about it during the interview.
The approach I took when dealing with these sorts of questions in my Stage 1 interview was quite risky, not sure if it will work everytime when used. When they asked me what I liked about the 777, I told them that my love for the aircraft stemmed from watching the aircraft take-off and land. I said that I did not know much about the internal systems and as such they couldn't be the reasons I liked the aircraft, as obviously I have never flown a 777 and cannot appreciate the level of technology onboard. They seemed to accept the answer but I am quite sure I will be drilled on 777 tech if I make it to Stage 2.