Thunor,
It's quite usual for them to interview a whole bunch of people at the same sitting. At my own, there were perhaps 3 or 4 potential commanders (all of whom were offered jobs on the spot, BTW) and well over 20 brand new FOs. The 'presentation' is a 'powerpoint' job that lasts about 15 minutes and gives fleet numbers, future plans, etc. It's really just a scene-setter and makes Don feel clever!
It'll be interesting to hear your experiences when you've been, but I would be 99.99999999999% sure that you'll come away with a job offer and a start date.
Worth keeping in mind for when you do start is that, although you will go through a full Q-400 course, (you'll need it, it's a very different ship, ie FADEC, for starters) strictly speaking you are joining as 'type-rated' since you don't need anything else on your licence. Therefore, your bond should only be for £5000 over one year, and not £15000 over three. (This is not a secret, or a special deal BTW, but black and white in Company NOTACs) Point this out to personnel when you start.
Good luck. Let us know how you get on.