OK, maybe I've read the thread too fast....I don't loose the accessory mode if I move the selector from N to P, power just stays there. So the use case would be as follows:
1. Driving and listening to the radio or talking on the phone (via the BT interface of course)
2. Arrived at destination but want to finish the call without switching to the handset.
3. Move the gear selector to N, push the red button - engine shuts off, power stays on so I can continue the conversation.
4. Move the selector right away to P and apply hand break - power still stays on.
5. Conversation finished, ready to go - push the red button, everything dies, open the door, driver seat moves all the way back.
Apologies if I am stating the obvious but I am a bit confused....