I agree with Austman and PeterC:
1) The OC is not obliged to bring an old building up to current BCA standards.
2) But I can’t see any valid reason for refusing permission, as long as the lot owner pays.
3) The work should be done by a professional. Do you really want to electrocute yourself, or burn the whole building down a few months later?
Scotty,
a) How much did the roof void vacuuming cost?
b) Wouldn’t the sarking exercise be more costly than the batt insulation? To do it properly, they would have to remove all tiles, lay sarking, probably with all new battens, then replace tiles.