I have always assumed the resistor things are to produce the variable speed for the ventilation fan (the one above the heater works) and the wipers (the one on the strut turret. I've never known them to get hot and, assuming they are what I think they are, there shouldn't be any power to them unless the wipers or ventilation fan are operating.
The rear light without a reversing light is interesting too. Did it come from abroad? I can't think I've seen a UK car without reversing lights on both sides. Even the poverty spec one for sale on e-bay at the moment has two. My spares have a reversing light but I'm scraping the barrel for unbroken ones now.