I think a strongly worded letter from your strata manager or lawyer telling the developer their contractors need to respect their neighbours and, by the way, you will be raising the issues of overshadowing at a strata meeting to see what action your scheme can take to mitigate the effects of their construction and determine if it was legally approved.
Something like that to fire a shot across their bows. Remember what happened at Mascot Towers – it’s very likely that work on the adjoining lot cause the building to collapse.