Sorry if this is a bit late, but maybe it can come in handy for someone else.
I was interviewed in a small office by a board of no more than two persons, and they were both superfriendly. You will be asked to give them examples from times when you were in situations where you had to deal with certain circumstances.
You were given some information with the invitation to the interview. That info is pure gold. Those specific circumstances are in there. Match the question areas to the pqa-descriptions that are in the application pack, or on
http://www.fireservice.co.uk/recruitment/pqa.php Here's an example:
If you are to be questioned on Confidence and Resilience, you'll find the criteria stating: "Maintains a confident and resilient attitude in highly challenging situations. Remains in control of own emotions during emergency situations, does not panic and considers risk. Concentrates on the task despite pressure" etc.
So start thinking about a time when you were in a situation that corresponds to as much of the criteria as possible. Like the letter says, make sure to include in the story how you contributed to a successful outcome. Find a story or two for each area that will be questioned.
Hope this helps and good luck!