Don't forget the roof - that's where most of the heat goes out.
I removed the carpet-lined trim panels, stuck on the foil bubble wrap, then replaced the panels.
An easy job, and you can do it one panel at a time - and consider if you want to rewire / relocate any of the lights at the same time.
Hi. Second time I've put this link up in a week. Last time for noise reduction. The article is really focussed on heat retention so ideal for you. It is all based around a type2 but applies equally well to a T25. http://www.type2.com/library/heat/heat-soundproof.html" onclick="window.open(this.href);return false;