I built a single storey extension within the guidelines for no permission (3 metres out, 4 metres high). Had no problems till the neighbours moved in and reported it. Council are aware it's within the permitted measurements but have said I should of told them before commencing work and I now have to apply for permission. My neighbours will definitely object! I'm not sure what to do from here. I honestly thought we had done it all correctly. I wasn't aware we had to inform them but am in a no win situation. Can anyone offer any advice please? Thanks