2007 RR SPORT L320.

The drivers door window master switch has stopped working. Some of the other windows work on their own switches, some don't. I've tried another master without success. I've read that the BCM can sometimes be affected by water ingress - stupid question but where is it and are there any go-to's to tackle this problem?

I would be more concerned at wiring n the door hinge area.

Also check there is power to the motor on thick wires.

The RRS doesn't have a BCM as such. In the workshop manual, "body control module" only seems to refer to the suspension and steering ECU which is on the driver's A-pillar behind the dashboard - accessible from the footwell by removing the panel above the pedals and reaching up.

You could get water near it if you have a sunroof with blocked drains or a poorly installed windscreen, but other than that, I don't see how you'd get water near it. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

At the front window motors:

The thick Green wire should be +12v all the time.
The thick black wire is ground

Check there is 12v between these 2 wires. Open and close the door while ensuring these wires have 12v between them all the time

The thin black wires should connect to ground when the drivers window switch is pressed, to command window up and down. So check the switch is doing this.