sorted: Cement board (fire board) - min. 75cm x 20cm.

[KidKruger]

Ideally local suppliers either don't have it or have only 8ft x 4ft sheets.

I only need enough for a register plate inside a chimney breast - so need to cut a piece approx. 75cm x 20cm

Any thickness i.e. 8mm or 12mm should do the trick.

PN pls

[KidKruger]

sorted - cut the register plate out of steel instead.