Unless the law has changed you can take the following to the bank if the work is wholly within the lot.
Or even outside the lot as my stratas have discovered.
Planning approval is one thing. Anyone can pay the application fee and tick the boxes which inform the council that they either own the property or have informed the owner of the property (even if they haven’t).
And they might get council planning approval.
But AFAIK, actually altering property that you do not own is still illegal.