I agree you cannot wheel clamp or tow from common property or visitor parking bays, but this is actually ON your property that you are paying for so advise the offending owner in the nicest possible way that the next time your bay is obstructed and you require it you will be getting a tow truck to remove the offending vehicle.
Whether this is legal or not I don’t know ( but I doubt the offender would either) and the prospect of loosing his car might encourage him to stop offending.
Phone a tow company up and ask them what is the rules regarding removing cars left on your property. The will def know.
You might also suggest to your property manager a rent reduction for the parking space you are unable to use. This might make him contact the Strata to get some action against the offenders.
Police and council will not be interested, it’s strata responsibility.