I thought about the ashtray idea but in the end I went for the cigarette lighter option as I don't smoke. I put a simple switch for the Ignition switch in the switch panel directly next to the new starter button and simply ran a bridging wire to make the starter button live when the ig switch was activated. Been like it for 2 years and all is well.
I only did it cos my ignition barrel jammed. Still need the the key in the barrel for the immobiliser and you never know the barrel might un-jam one day and that would be scary at full chat if the key wasn't in
The only problem was that I then had nowhere to plug my sat nav in so I had to hard wire it and that opened up a whole new can of worms, but thats another story
97 hell red 328i, M3 front, Eibach springs, 18" dished Alutec schnitzer typeII replicas.