From what you have said I take it you are a tenant.
Of course you have the right to control what goes on on property that you are paying money for, perhaps most importantly you have the right to peaceful enjoyment of the property. That includes not having contractors appearing outside your bedroom window over a prolonged period.
Whether or not the balcony structure is common property, you are paying money for the use of it. As you said, it is part of the premises you rent. The issue is with your landlord who should then take it up with the OC.
As you are not an owner I suggest you serve notice on the landlord that you do not accept the situation and you refuse to allow access to any contractors without appropriate notice, and that access will only be given where it is reasonably required (in other words, they can’t just use your balcony because it is the easy option). You can give a copy to the OC at the same time.
Note that under the Strata Schemes Management Act the OC can require that an owner give access to a property, refer section 122. But that doesn’t mean they can do whatever they like.
I also suggest that you tell your landlord that you would like a retrospective reduction in rent, I am not sure why you didn’t take them up on the offer.