"Tim S" wrote
| c) Does having an endothermic but still combustible material
| like celotex packed around electric cables bother you?

The electric cables will have to be derated for running within insulation.
Lighting cables on a 6A MCB are probably already fairly generously sized,
but 2.5 ring circuit cables willl almost certainly require replacing with
4mm or worse (bigger).

Owain