Carrying on from what you have said yummymum is that there is no such thing as overcrowding anymore within the council, as livingrooms and dining areas can be turned into bedrooms and there is no limit to how many people to a room.
I was told this by a friend who had contacted the council trying to get them to evict her no good son who had decided to move back in with her (he gave her no choice) and take over her livingroom as his bedroom. She said there wasn't enough room as she already had a son and 2 daughter's including herself living there in a 3 bedroomed house. They told her the above. So it's doubtful that there is a law about overcrowding but you could ring your local council office and ask or someone with a bit more knowledge on here may be able to help you further :o)