Lots of confusion in this thread on what is insulation and what is cladding.
ACM does not attempt to provide any insulation properties. The PE core is a structural part of the panel and at 3mm thick is not designed to provide any insulation.
The insulation properties of the wall construction will be provided by the insulation product used behind the cladding and ventilated cavity.
A class 0 rating refers to the speed at which a flame spreads across the surface of the product and isn’t related to how combustible it is. In the case of ACM, this will be how fast a flame spreads across the surface of the pvdf coated aluminium external skin of the material, not whether the core material itself will burn.
Approved doc B places limitations on the combustibility of insulation and filler materials used in external wall constructions when a building has a habitable floor level of more than 18m above external floor level (unless another route to compliance has been sought).