wood/coal burning stove - what material to board around the flue? (was asbestos)

Traditionally Agas would have a cast iron flue with no boarding around them - you know it's hot and don't touch it. Nowadays it's also common to use insulated stainless steel flue pipe (more with woodburners than Agas), which considerably reduces the requirement for fireproof materials close to the flue (it's expensive though). But if you have to board around a hot, uninsulated flue, I'd look at the various cement boards available (similar to plasterboard type material). What supported the old asbestos boarding - wasn't fixed to wooden studding was it? Building regs have things to say about minimum distances between flues and non-fireproof materials.