Hi guys,
Sorry I've been too busy to read through the thread properly, so apologies for any advice already given being repeated.
I can say that Social Services would very likely consider these children old enough to be left left on their own, especially as the 18 year old is an 'adult'.
You've gone the environmental route which is good so I'd say the next step is to report them to the council for being bad neighbours. You can report them to the housing section even if they are private tenants I think, in which case you should also write to their landlord hun. Housing people make a lot of noise these days about nuisance neighbours and Asbos.
Also be sure to keep a log of time, dates, etc about the neighbours noise and also so another log for conversations with anyone you speak to on this matter, including the neighbours.
I hope this helps sweetheart.
Much Love,
Tiff xxx