If you open the bonnet and use the arm to keep it open, as you look on top of the rad, there is a plastic box section that feeds the air intake. Don't know if you've noticed the bodywork in front of the rad it has slots on the left hand side, to feed air into this box arrangement. Just behind the air intake which is on the left hand side, there is a cover and under that there is a plastic flap that easily opens if you just blow through. So if your just standing still the flap won't open.
Is this to do with letting the engine warm up quicker while standing still. I don't have a clue, what's it for, does any body know