Sometimes leave mine down on the drive, you do have to be a bit careful living by the sea, sea gulls can make a hell of a mess.
Having said that they can just as easily drop there load on you when driving with the roof down as they can if you are parked.
Not had it happen in the Zed yet but in my previous MG TF pulled up at a pedestrian crossing on Torquay sea front earlier this summer, a low flying sea gull dropped its enormous load it hit my head rest and splattered all over the folded down roof, all over the boot lid, back of both seats and yes all over the back of my head

it was highly embarrassing and a right mess to clear up