Motor unlocks pins, hydraulics lift plastic clamshell lid. If it doesn't unlock, a red flashy light appears !
I've spent most of the last 45 minutes reading about the system in the service manual... whew...
I worked out that mine doesn't have the LED beside the switch... I have an LED in a similar place, but it's for the aftermarket alarm.
Anyway, the system has a motor on each of the rear pins, mounted on the lid. Each of these leadscrew assemblies has a microswitch with two contacts - one to signal the approach of the pin as the "5th arc" lowers, the other to signal when the pin is locked. On mine, it is these motors that are noisy - maybe time for some adjustment/lubrication. When the lubricant gets into the microswitch - well - that will be a nice day as the control unit won't know when the hood back edge is locked. This all seems rather like aircraft landing gear problems, though at least I won't be circling above an airport waiting for the 'gear locked' light to come on...
The motor with the plastic gear and the cables just releases the catches for the hood cover, as you said. There are, of course, more microswitches to register when the catches are locked.
The hood cover lifts with hydraulics. The hood folds or unfolds. As the 5th arc lowers, a "ball switch" (looks like a manual gearbox reverse-light switch) triggers when the mechanism passes a certain point. The control unit then activates those noisy leadscrew motors before the pins approach, to improve their engagement. This explains why the motors activate before the pins get near, I thought perhaps that was a fault.
I didn't know there were two motors in the lid for the pins, plus the motor with cables to release the hood cover (but not to raise it)... and there are many microswitches... I thought some of these functions might have been doubled-up (e.g. by having the lock pins also lock the cover down) but instead everything is separate. It doesn't look like the easiest/cheapest way to do it, that's for sure!
Off-topic but the other day I replaced the microswitch that registers when the bonnet is closed (under the left-side catch) - the microswitch was a good-quality sealed type, but it had lost its click (something broken inside). I imagine if the hood mechanism uses similar microswitches, I might be replacing them too one day
On the models with manual hood, there are electromagnets (solenoids) to release the cover and the pins, rather than motors. These solenoids have strings to pull in case of emergency. The motors don't. However, maybe the leadscrew motors have proved reliable.
The reason I thought the hood cover was plastic is because the paint has faded to a lighter colour than the rest of the car
The part inside the hood is the original colour, so the difference stands out when the hood is down. I guess I shall have some fun repainting it once the summer weather kicks in - the question is whether to try and remove it from the car or mask off and paint in situ...