Thank you all for clearing things up.
Its annoying to read that they offer 42 days of leave which sounds great, but now with your explanations i doubt the integrity off the system, yet the number of days i will actually be able to get. I am also surprised that you can only take a maximum of 4 periods of leave. All these problems really limit the way you can use that huge entitlement of 42 days.
It sounds more like leave is just a way of getting guaranteed days off especially if you say you can still fly to the maximum hours and the fact that there are no wrap around days. It seems like leave is what it would have been days off in a month, but you can hope to control your days off at 4 times in a year.