cold starting/running & 480 interior light

Can someone tell me how the interior light is switched when the door is opened? No switch can be found and it won't work. The drivers door lock light has been disconected for some reason is that connected? What signals the interior light to come on could it be the central locking even? It works manually only now.
Also on the 480 es Auto it has started running badly on start up when cold and it won't run well until warmed up. This happened overnight so what could have failed as it was fine before. Is there an automatic choke of some sort?
I'm new to these strange cars and I have to maintain my mothers car hence all these questions.
Cheers H

The interior light is tied in with the door lock/handle circuit& therefore if the lock light has been disconnected I think that it's safe to assume that this will also disable the interior light(just been outside & played with the lock to confirm this!)
Mike S

Thanks. Now how does it connect up? There are several spare multi block connectors in the door base and just one white wire dangling free from the lock which must be the lock light? So which wire should it connect to? Have I some missing?
The central locking is still working but the alarm dosen't so that probably uses the same circuit.
The car has had a new door at some time and obviously was never fully connected up by the repairer before we got the car?
Anyone got a door in bits to check this out and tell me where the white wire connects. Car is 480es Auto H reg.
Harvey

I've solved it! The plug under the throttle body which connects to the throttle position switch was the problem. It looked clean and corosion free but I cleaned it with WD and the problem has gone and it starts fine again now. You need to prise out the spring clip around the plug before it will undo. Still got the light to connect up yet. Anyone with a scrap car that could provide the loom from the door lock/handle to the main door loom as mine is missing.
H