I have several consumer units around the house but before them all is a new 100ma 100ms RCD in a box, so must only this box be insulated?
ukdiy wiki says: "With a TT install you will need to use an insulated CU since this minimise s the possibility of a phase to earth fault occurring inside the CU before the RCD (which due to the high earth fault loop impedance of the local eart h spike, may result in a fault that would never be cleared). " at