Easy Flameout ,
I went to the Easyjet Assement day 2 months ago and here is what I can recall from that day :
a set of technical questions such as about mach tuck, some met questions ---> I suggest you read "how to ace the pilot technical interview " By Gary Bristow, everything is in there.
some psychometric test ---> Nothing you can prepare.
45 minutes interview, quite relaxed. They asked me some questions such as : " Can you remember a moment in your life where you have taken a difficult decision" or "have you ever worked with a difficult individual, how did you manage to get his co-operation " ... My interviewers were very nice and gave me the time to think before answering. Also they asked me some technical questions too. One I remember of is " what gaz do we put in Aircraft tyres "
The whole day is fairly relaxed and they definitely try to make you at ease, so you can give your best !
Good luck, SF