I have similar in Rover 400.
Rear door switches were corroded, just pull tops off (mind the springs) and clean contacts & Wd40. Put a multimeter on it and check just a simple On-Off.
But turned out to be the one on the bonnet catch which ment taking off the front bumper (not difficult) there is a micro switch right in the center of the catch mechanism with a little lever arm. Mine was gummed up with grease. Again simple On-Off check with multimeter at the connector. If not work bung up the horns.
Kryton
March 2007