Neighbours house renovation not legal. United Kingdom England

Hi, my neighbours have been working on their house for almost a year. Recently the bad weather blew down a few of their back garden fences. It revealed that they’ve added 2 additional doors to the property. Both doors are ‘ front doors ‘ it looks like they’ve sectioned off the house into flats. I’ve checked online what the plans are and they don’t have permission. I contacted my local council and to put in a complaint I have to give my name and address. This wouldn’t be a problem but the family are loud and rude especially the husband. He’s argumentative and loves to piss off a lot of our neighbours. They own the property and we own our house and not in a situation to move in the foreseeable future.