Norrol,
I'm not sure me giving you my answers will be particularly helpful... they want to know about you, so you need to be able to talk about your experiences and why you want to be an ATCO.
To be honest mate I think you're overthinking it a little. You can't have the entire interview rehearsed in your head before you get there because you never know exactly what they will ask you or how they will word the questions. Just think of as many solid examples of situations and circumstances you have been in to do with the various competencies and you'll do fine. At the end of the day if you have what they are looking for then that should shine through, if you don't then it won't, you need to prepare but you also need to realise that you can only do so much and that they will always throw one or two curveballs on the day that are designed to put you on the spot and will be things that you won't have prepared for before hand.