I live in a large single floor (like a bungalow) style building split into two separate flats which share a hallway and main front door and back door opening on to gardens. The flats are self contained but entrances and exits aren't. There is a building owned by the same landlord attached with a same set up. Due to the set up the post box is shared too. This is all relevant.
Two weeks ago new tenants moved into my building. They have been okay apart from very very loud music which doesn't particular bother me as the bedroom is at the far end so I can cut a lot out once I'm in bed and my kids sleep through anything but my neighbour is in her 80s and will complain. I am a single parent with two young children and disabled.
So far so boring until a friend came over to visit today and bumped into them in the hallway.
She recognised them and later told me that the main tenant and one of their friends had recently been in prison for a violent unprovoked attack involving weapons on an innocent person on a night out and had a string of previous convictions for physical violence usually on a cocktail of drugs and drink 
I've searched this and its all correct. So as it is I'm now sharing all entrances and exits with this person and all their mates who are frequently over.
I'm now worried sick and just feel trapped. I'm frightened of my elderly neighbour complaining and me getting the blame for it. I'm frightened of them kicking off for some reason, of my children sharing the hallway and garden with these people.
I can't afford to move at present although I'm trying to save.
Do landlords not do references checks usually?
If you were a landlord would you really not care enough to put someone like this in with someone vulnerable.
Aibu and over reacting?