The film that you can get to block the light and cold works better, Sorcha. You put it right on the windows. You can cut it to size and reposition it. I used it on those west windows at the house you all came to when Bill and Allan were there. Got it at one of the lumber/home building outlets downtown. My plants still got plenty of light and we were able to see out of them just fine.
We put space blankets up on my brother's walls of his apt. because there is no insulation. We also have them in the car for emergencies. Once they get a cut or tear, hey rip fairly easily, so I don't think sewing would be a good idea, likewise washing.