LFB report in 2011 suggested main cause was poor connections to neutral
busbars. See
http://www.electricalsafetyfirst.org...ched-On-25.pdf

Included:

"While the main cause of fire within plastic consumer unit enclosures
is without doubt poor workmanship, the materials used in the
manufacture of such enclosures and possibly the type and
arrangement of the components are other factors that can't be
ignored. The increase in the number of terminations having only one
securing screw and an almost unanimous adoption of 'cage clamp'
type terminations are arguably a backward step in equipment design,
irrespective of whether they comply with current product standards."

and

"Five common brands of consumer unit were selected for the first
stage of the investigation. Initial tests showed that only two of the
five brands included flame retardant in the plastic enclosure material,
although there is no requirement in the applicable product standards
to do so."





--
Robin
reply to address is (meant to be) valid