"I suspect the Council deliberately houses certain types in these places 'to keep them all together'"

I've no idea whether that might be true or not to be honest. I guess it's possible, but baring in mind that much like those who work in other social services people who work in social housing tend to do so at least in part due to a high sense of social responsibility, I have trouble with that notion. My old housing officer for example was a Marxist, I rather doubt that he would have subscribed to any such practice! Basically housing stock is impossibly limited, there isn't any left, so what there is is almost exclusively allocated to those in greatest need. Those in greatest need will be those with a number of children, people fresh out of nick, the disabled, those living on the street and those with mental health problems (not unusual to find several of those things going together of course). As I said before however, you will see a certain amount of 'self selection' going on, particularly if you're a social housing tenant who's ever been involved in exchange schemes: "i hav luvly house wiv nice size garden, new bathroom and kitchen. want 2 go to bluebird way". My old estate was a grotty place and notoriously tough to get out of, there was car theft and some knife crime, drugs of course were available if you knew who the local dealer was (as everyone did) and to top it off a child sex ring was found operating there. The people we finally exchanged with wanted to live on that specific estate to be near their friends. Even though one might wonder, there's nothing very shocking in that really either - after all we all want to live somewhere we feel at home.