Thanks to all for the replies.
I was able to return the megaprim - what remained was a small lot with a house and yard, none of which impinge on my property.
Wulfie, at the moment it is not effecting my visual airspace, that is I cannot see it from the ground nor from my skybox at 2000 m. However I plan additional development at 1000 m and 1500 m in the future and it's probably best to get it resolved now.
Cheers.