There is still great confusion all around here and IET has yet 'to my knowledge' to give a definitive response to the questions posed to them about the confusion of this regulation 421.1.201
Here lies the problem - The consumer unit or similar switchgear has to comply to BS EN 61439-3 with basically is a set of test like an hot touch, self extinguishing etc...
As worded by the regs -
Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 AND SHALL;
(i) have their enclosure manufactured fromnon combustible material, OR
(ii) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with reg 132.12.
NOTE 1: Ferrous metal , e.g. steel, is deemed to be an example of a non-conbustible material
NOTE 2: (Just mentions implementation date jan 2016)
Now the problem here is the regulations states it has to comply to both the BS61439-3 and be non combustible if you do not house it as to point (ii) but there's no documented definitive definition of a non-combustaible material but they do give an example so this is not saying it has to be steel.
My next point is everything is conbustible given high enough temperatures and the conditions to burn so we need to know the exact requirements to be given a non combustible rating are.... all the manfacturers have to comply to is the BS 61439-3 and that allows them to meet the first part if the regulation but who is going to define the parameters of the word non combustible, yes steel is an example but as this is the only example they give we are stuck with the example as we have no other information to go on.