Also, you'd need to get marginally creative with the back seat in an M6.In the olden days, it was considered a convenience (if not a necessity) to have a live cigarette lighter for lighting up when parked, such as when having a smoke after sex in the back seat. [Refer to fig. 1 below]
Today, as smoking has become more politically incorrect, and drive-in theaters have gone tits up, most lighter sockets are used for other purposes, or not used at all. So the manufacturers no longer provide it as a hot circuit.