I wouldn't worry too much, its quite normal, as long as the car raises once started. The car will prompt you if its too low or if there's a fault in the system. Cold weather will make it drop a little faster than usual. Hope this helps.
Thanks, and is it normal for the car height to lower as soon as you remove the key after a drive. I would have thought it would have stayed raised for a few minutes just in case the driver might want to go for a ride again.