Just a few things, although obviously Council approval is relevant.
– you say that the Committee passed a motion banning leasing of the units. PeterC may be able to enlighten us as to how it works in Canberra, but I would assume that anything like that would have to go to a meeting of all the owners to have any effect?
Did you get notice of the Committee meeting where they passed this motion? For something like that there should have been a notice with the intended motion on the agenda.
– re retrospectivity, as a general rule it applies from the time the rule applies, so any action that breaches that rule from that time on is a breach of the rule.
– the amount of money you may have spent furnishing the apartment isn’t really relevant.