Ask an Property Solicitor. Get an Answer ASAP.
It was built before we moved in about 18 years ago, however the guttering has since been replaced but it extends further out over my roof than the previous guttering (which did not). When we moved in, we had problems with water coming into our bathroom so we checked the plans and contacted the council who agreed that the extension was not what was on the original plans but as permission had been granted there was nothing they could do. The extension was built on a flat roof and extends 1 metre above my property.
No I haven't spoken to my neighbour about this yet!