thanks for the tip @nod. i did another search through the BG website and found this image for a secondary dropped ceiling.
so it seems that the FEA1 steel angle is screwed through the plasterboard into the MF5 channels above allowing you to to repeat the ceiling below.
so this will double the cost of the MF materials but give me an unbroken ceiling to reduce noise transfer above.
i think this is what i'll do as it also means i can fit, insulate and board the primary ceiling without worrying about running cables before hand.