I built the current heating system after experimenting with a standard mini heater which proved insufficient for de-misting.

I based it around a Ford Escort 3-speedblower unit, interior directional vents, switch and the mini heater matrix.

I made the box up out of a sheet of Aluminium, forming it around a wooden post.

Above, you can see that it is all quite stealthy, the blower unit is mounted behind the stereo head unit and blows air up into the heater box, through the matrix and either via the interior vents (if they are open) and always up to the demister vents.