I will unplug mine this weekend and see if I can get reception still.
My aerial was permanently in the upright position. At the mo I just turn the car off, whilst the aerial motor is whuring away trying to decline, I smack the top of the aerial down with the palm of my hand. It takes one hit that is firm but not overboard, then it picks up on the teeth in the motor and goes down. The other way that I first used was to push it down, but the smacking method works for me best as it wont snap or bend the aerial.