If the screens are on common property, and are furthermore not in compliance with a by-law, and they have given more than adequate notice to residents to retrieve their property, I can see no impediment to the EC simply going ahead to remove the items unless access to these areas of common property is only possible via a unit area. That complicates matters since I expect the NSW legislation and/or your by-laws have other regulation about reasonable notice and purpose to enter the unit. That could be the next step on expiry of the 30 days. To save EC members some personal grief, it could be best at this point if you have a managing agent to ask the agent to engage a person to do the removal following proper notice, to the letter.