I fully agree with Billham in that if you go over to them and start making an issue of it then you will escalate matters further because they've got a reaction which is the seed planted because now they'll have a focus to vent their anger and boredom at. If they're smoking cannabis then they're probably going to be alot more amiable than a load of England fans in a foreign city trashing the place so in that respect you're getting off lightly. There is however a fine line between tolerating it and being made a prisoner in your own home, a friend of mine suffered exactly the same problem. She decided along with other residence to play music that she knew the pests outside wouldn't like (hoodies don't like classical music or opera) and after a few nights of her taste being ridiculed they eventually moved on.