Is it ok to keep chickens in your flat?

Ok so my landlord allows pets. I want to fill my flat up with chickens and chicken pens. I have already got 5 hens and 2 cockerels and there are more eggs waiting to hatch. I don't own much electrical stuff (apart from my laptop), so there is lots of space. They are happy as can be and have water bowls and feeding troughs in here. Sometimes when I am in bed at night some might come and sit beside me.