Thanks for the responses. The item seems to be a half inch thick laminate with the two outer layers some sort of filled mesh with polished aluminium facing and a sandwich material a type of 'rockwool' insulation matting. I really have no idea how to fabricate this; perhaps an aircooled Porsche has a similar item, certainly Puma was trying to mimic a quality item. Martin Davies

My firewall, and others I have seen is only about 1/8 inch thick, just fiberglass only. Then the both sides have an "anti noise" insulation pad attached.
Your description sounds like some type of aerospace laminate. Is it possibly not original?