[Ant]

I have used Kawool, not sure how you spell it, but its white and a bit like fibreglass batts, quite dense will never burn, can be wrapped around a boiler stack etc.

I made an aircraft alloy firewall with 5mm stand off bobbins and fitted Kawool behind it - absolutely NO heat gets through....period!

Another way maybe a good fireproof silver side heat resistant material, that can be glued on and supported by alloy strips either riveted or whatever, like a lot of original Cobras have around the foot box.