I went to their interview last year and I thought it was a complete sham.
Its extremely informal... basically they split a room up into four sections, put a table in each corner of the room and called you up. Whilst everyone else was in the room, ie. applicants and parents with loads of noise going on in the background. I thought it was really badly organised, and that lack of organisation made me realise that Kingston was not the place for me.
So basically do not be worried at all... if anything its a good thing to go to the interview because then you will be put off like i was. Kingston is only useful for an insurance.
In other words, dont panic it will be fine and they will probably give you an offer.