i have recently started IOT at cranwell. In the interview i think that they were more interested in what you think an officer does and is, rather than your role, you are an officer first, pilot second. They want you to be confident, you are supposed to be able to lead people, not much use if you cant even speak up in an interview. You should have been given a load of blurb when you went to selection, in that there are a list of qualities that an officer needs to possess, i.e. integrity, teamwork, smart appearance, puctuality, dtermination etc. They want you to know about these, and to be able to give examples. Some advice given to me by an officer, that they like to hear in interviews, is that being an officer is more a lifestyle than a job, they expect you to behave in a manner befitting an officer at all times not just while at work, obviously there will be loads of people laughing at that cos no doubt there are loads of NCO's who know officers who act like tits both in and out of work, but they want to hear it all the same. My main bit of advice is just to be confident, not arrogant, just let them know throughout the interview that you know in yourself you are capable of doing it, not that you are trying to convince them that you are.
Good luck mate
P.s. Dont waste the time sat on your ass, they will also expect you to do better in the fitness test as well.