You can get done if you sleep in the car after a night out, for drink driving, if the keys are in your possesion, even if they are not in the ignition. I have friends that used to do it, so that they did not drink and drive. Unfortunately common sense no longer prevails.
I know one guy who has done it recently the police knocked on his window, they were going to do him but could not find the keys in his possesion, so could not charge him.
He had hidden them nearby in a flower bed, so he would not get done
It is the same as you being done for talking on a mobile if the engine is running, even if you are parked up and out of gear
Yet again the law is an **** and common sense seems to be lacking