Simon:
Mine is a 64 plate Mega Space. On the side of the centre console in the passenger foot well mine has 2 ■■■ lighter type sockets, one above the other.
The top one is 24v, the bottom one is 12v.
There’s another socket in the dash, next to the passenger pointing middle air vent, that one is permenantly on.
The easy to see socket on the drivers side of the curved console switches on and off with your ignition.
In the 14 plate I had, and the 15 plate I currently have, it was/is the top one out of the two in the passenger footwell
The company I drive for, run a lot of mp4 mercs, and the switches are all in different places
This can be rectified by removing the banknof switches from the dash, and pulling the switch out of the back block, and then, you can refit it in whatever switch position you like
To get the switch Banks out, pull out the silver end plates, then push them apart, as pushing apart, pull it out of the dash