Thanks, Matt, I am interested in this to get a better idea of its performance. I’ll drop you an email about that, sounds like getting it over the winter will be useful!
I did get a foam insulator to tell me he could foam fill the cavity as that would exert pressure against the foil and avoid areas where the foil may create a void. However, I wasn’t too sure about this plus he quoted £10,000! not a chance I could ever recoup those costs in any meaning full time.