I thought it was/is the BS7671 we need to consult, not the NICEIC.I actually brought this up the other day down at the NICEIC/ELECSA Tecktalk in Brighton the other day (bunch more scheduled for other parts of the country if you're interested). The big wigs there were of the opinion that although the regs suggested ferrous metal this was simply due to other sufficiently non-combustible materials being unavailable, and of about 2 dozen stands there one of them was showcasing a non-metal non-combustible gland kit designed for use with amendment 3 CUs. If that works for the NICEIC that works for me.