neighbour's building work exceed size granted via certificate of lawfulness - what to do?

Hi,

we've got ongoing issues with our neighbours who run the house next to us as 'slum landlords' and do rogue building activities.

I'd posted a few months ago and the beginning of the story can be seen here: http://www.harringayonline.com/forum/topics/illegal-hmo-what-to-do-...

Basically they're running an illegal sharehouse next to us that was at most occupying up to 17 people in a 4 bedroom house.

What we discovered now is that the owner (who's apparently a property magnate owning about 40-50 houses in North London) is increasing the size of an outbuilding to bigger than agreed. The certificate of lawfulness should allow him to increase it to about double the size, however he seems to build to triple the size. What he declares to be a 'gym and games room' is rather a one bedroom flat with a huge foundation and running water.

So far he's very much neglected all rules and regulations of building law, e.g. he tore a wall down right next to our house and made a hole in our kitchen wall claiming it is his. He only agreed to get a survey done when we went to court requesting an injunction.

Has anyone come across a similar case? We've been onto several council departments due to various problems, but they surprisingly turn a very blind eye on the case. There were only controls when we and other neighbours reported an issue and continued banging on about it literally for months until they took action. However even this didn't bring any solution (e.g. we were reassured that the house would be vacated by end of May but there's still people living in there.)

Any advice is much appreciated - obviously we will report the issue to the council again but we're just wondering how to best deal with it and what action the council is most likely going to take.

Thanks