The none if them worked maybe the problem isn't the garage wall after all. Re porous breezeblocks, some of the recent type are used because they are supposed to have good thermal insulation properties. (Lord knows they're pretty useless compared with traditional bricks & mortar when it comes to fitting anything to them.)
Try checking your other kitchen walls and the roof space. Or even whether your heating system has a powerful enough radiator.
As for that foil stuff, I'm sure you could, I don't think it a great idea. You'd have a kitchen with a reflective yet easily damaged surface. (And not sure if the steamy atmosphere would have a good affect.)