apples45 – it is generally accepted, and apparently confirmed by your own research that power outlets within lots, safety switches on power boards within lots, and hard-wired smoke alarms with lots (that are not connected to a central control board on common property) are all the responsibility of lot owners.
In that circumstance Sect 63 (4) of the NSW Strata Schemes Management Act (1996) could be used as the basis for your Owners Corporation (O/C) to recover from lot owner/s its costs to carry out works that would otherwise be the “duty” of those owner/s.
The only “hitch” in applying that provision literally to your situation is that the Fire Order requires the O/C and not the lot owner/s to comply, although I’d interpret that more generally as the Order requiring the O/C to ensure that required works are completed and certified as compliant.
Nonetheless, and particularly as none of your owners responded to the earlier letter and I interpret from your posts that all works have been completed (?), I agree with that part of larry’s advice (post #4) about putting the whole thing before owners at the next General Meeting, possibly including an option that the O/C pays and reimburses those owner/s who have already made certified changes to their lots.
Not so sure about legal opinions in this case though; give “strata democracy” a chance!
Whatever the outcome, remember that whilst your Strata Manager may offer advice and opinions (albethey conflicting) there are no “battles”, as he’s required to act in accordance with the directions of his client (the O/C) provided those are in compliance with the Act.