Have got afore mentioned book now, and revised my plans.
Current best plan is to make inner lining from night storage heater bricks, and outer lining from perlite / fire cement mix.
It seems that the perlite probably wont stand up to the temperatures involved for the inner lining, and possibly wont for the outer either - however, if it burns out in the mix, then i cant see that being too much of an issue, as all i want on the outside is insulation (if i had cash to throw at it, id use ceramic blanket)
