Unlike James that used kitchen foil in the heating unit, I am getting a galvanized flume (if that is the right word) made for my heating unit.
I picked up a wall mountable 2 bar heater today (hope it will produce enough heat) for $15.00 [new]. I chose this unit because it was the only one without the tilt sensor [mercury switch?] which would prevent other units working on their backs. This one even has a small stand, so the unit is actually off the floor by at least 2".
I also got a quick over the phone quote where each piece of 0.6mm gal is less than $7.00 per piece cut and supplied and they can even bend the ends to 90 degree for me.
And about another $30 for the MDF box it goes in.