I'm using a PWM motor controller to drive my heater fan; it takes a 12v feed & ground spliced into the lighter socket wiring with the positive line via the panel switch. I picked it up from Ebay and its good for 10amps @ 12v which should be plenty for the heater fan - it will take out the lighter socket fuse before it gets anywhere near that.
The rotary knob on the side varies the fan speed but I'm expecting to leave it set once I find an appropriate speed:
I was so focused on mounting the fan controller board and wiring it I didn't even think to take another ground line for my boost/map button ! doh!
The only button with backlighting will be the fog lamp switch - IVA requirement, the others will have to wait until after IVA when I feel like re-wiring this panel.
All out of spade terminals now, I must be getting near the end of the build I keep running out of parts.