DH and I work full time and are up at 6am Mon-Fri.
My DH and our 2 DDs (4 and 7) live in a semi-detached house which has been built without our stairs forming the 'barrier', iyswim. Our bedroom is next to their bathroom; my DDs' room is next to their younger child's (18) room.
Neighbours have 2 adult (18 and 20-something) children living with them.
Their "children" bang doors into the early hours, play Youtube stuff at a volume that can be heard clearly in our rooms, play some sort of Call of Duty style war game so we can hear the bangs and groans and explosions... this frequently goes on until 2am. We can fall asleep, but then are woken up repeatedly throughout the night.
I approached the neighbours some months ago and explained that we could hear their noises and were being woken up, and to ask if they could be quieter past around 10pm. They were lovely, but nothing changed.
I went around again last week to ask again if they could be quieter. This time I was received a bit differently, with the father saying he couldn't "tell people what to do". One night last week, the noises were so loud that I went around at 1am to ask them to be quiet. The 20-something adult child answered the door, said they had all been asleep (!) and told me to get away from the doorway or they would call the police. 
Only one of them works; the others seem to mope around in dressing gowns all day when they eventually do get up. Would IBU to leave for work on Monday having turned my sound system on loud and directed at their walls from 6am?