12V THERMOSTATIC NIGHT HEATER

Very good, you might have it finished in 2025,   

Just a suggestion Tuggy, how about blocking the holes and making an air filter instead, something along the lines of a couple of multi layered chainsaw filters would give superb filtration and you just whip them out and clean them with washing up liquid and water. They work in the wet and cope with huge quantities of dust, and being a triple layered filter they filter just about everything out.