You can get foam cut outs the size of you box (double or single not sure about dual) that are designed to prevent drafts ,contain fires and help with sound proofing. i couldn't tell you what these are called but we used to get them from newey's.
hi i was just wondering what size cable and MCB and switch gear you would use for 8 400watt son t light fittings.
i have looked through regs but cant seem to find what page it is that states what current a type c/d mcb will take at start up
8x400x1.8/230 = 25A (x1.8 for start up)...