I went through the interview process 8 months ago and as stated it is very relaxed, but you still have to do well on the day or you will get the thank but no thanks letter from them.
Janine is excellent, really helpful and puts you at easy on the day,
we had 1 technical paper, 1 maths test and 1 psychometric test and the interview which was very relaxed.
Got through the selection and went into the pool for 6 months, I start on the B747-400 next month and can't wait.
On the day be yourself is the best advice I can give and a sense on humour goes a long way too.
cheers
fc