Amost posted last night, decided I was overreacting. Not sure now. Argh.
new family in flat upstairs - a couple and one child (apparently). Moved in on Thursday.
First night, more than them in the flat - a few adults and at least two children. Woman shouting constantly in a ranty way, barely pausing for breath from about 7pm (I study in the evenings and this is audible in every room in the flat). Sounded like she was shouting at the adults, they were replying in normal tones. Children were tearing round screaming and jumping off things (judging by thumps) until 11pm ish. Then the others left the flat.
Second night (last night) same pattern, except kids were running round until gone 12.30am, then child was whimpering, obviously knackered, and getting screamed at by women who was on phone (I was smoking on back step and windows open hence hearing whimpering, phone must have been on speakerphone. Having said that this is Victorian property where sound carries and at their volume it's really invasive).
Today since around midday there's been crazed sounding ranting/shouting/screaming constantly from this woman. Today they are definitely shouting at the child - man is shouting too, now and then. They keep doing a weird thing where they are talking (well, ranting) and shrieking every few sentences. There's been banging, some is clearly new flat type stuff but some is a bit suspect. There seems to be another woman up there too.
I'm shaking as this is setting off massive anxiety so not sure if overreacting but almost called police just now. Woman keeps going off on one, shrieking, sounds like maybe throwing stuff. They don't seem to talk at all, just yell. I can hear child basically mimicking them. And then they yell more 
. She sound like she might be mentally ill tbh, I don't say that lightly, there really is something that sounds overly emotional/irrational.
Now I've typed all that it's gone quiet, they are finally talking in normal tones.
Our landlord would kick them out for the noise alone, but I don't want to just run away if I can get some help for the child/mother.