i found this clip helped
http://www.youtube.com/watch?v=2FdoR6m4EDU
it helps to see exactly what movement your looking for, i was trying to push the screw drive too deep into the hole.
basically turn the flat headed screw driver so the blade is horizontal then push through the hole, but aim slightly towards you, feel about with a couple of pushes and wait to you feel resistance from the spring, once you ve hit it you ll realise and you should then be able to lift off that side of the air bag, if it doesnt just pop off by itself, it is a bit of a faff, but once you ve done it once, it will take seconds the time after that.