Jonah / Chiccy we had a similar problem with ASB and I found out that if things keep being reported sh*t eventually lands on a senior officier's desk "why haven't you stopped this etc"

Another worth doing is finding out who the neighbourhood inspector is for the area and badger them with phone calls and emails - it worked for my mate (the culprits eventually were evicted from thier association house for breaching their ASBO!).