Is the garage locked? Is the owner around during the day?
Seriously, though, the action in the Local Court under Access to Neighbouring Land Act 2000 may be worth filing and serving just to see the look on your neighbour’s face when they get it.
I don’t know the act and have no advice as to whether it’s the right one or not (although I suspect the Magistrate might see the words “Strata” or “unit” and send you straight off to Fair Trading). But you might be able to bluff your neighbour sufficiently to get a few hours access, rather than have them go to court. Or it may be your neighbour is a QC, in which case you are stuffed.