I going to answer my own question.
To remove the heater fan resistor switch:
Remove the screen from under the glove box - 1 Torqx screw on the left, a turn button in the centre. Once you've undone these, pull screen out of the locator slide on the right.
Find the red clip on the back of the heater housing and pull it down to release.
Remove the plug (the fan will now only function at top speed).
Look at the plug casing and there should be two empty screw holes (top and bottom) if there are screws in them (remove). The resistor switch is held by plastic clips (1 back, 2 front).
Release the clips and pull out the resistor switch (easier said than done). I released the back clip and by applying gentle pressure, managed to lift the switch housing out of the front clips, however, please be aware that you may bend the internals by doing this. I did.
Whilst you are down there it may pay to replace the heater filter. It is just in front of the resistor switch housing. It's the upright rectangular door with the diagonally opposed 6mm screws. Just undo them and remove the filter.
Ted, January 2009
