Is the developer well connected politically? I wonder whether the planners are stuck between a rock (local policy or national legislation that the build totally contravene) and the council (politicians beholden to or in cahoots with the developer).
I don't know how to do it but you need to force a decision out of them. Media might be interested in the occupied properties not having pp...
It is all rather suspicious. I do have my own view.
I will be in touch with my legal to try and get the Council to respond to the letters and make a decision. Failing that , I agree the media would love this story.