Sorry to hear about the issues that you are having. Bad neighbours affects your total quality of life. Seaford and associated suburbs are very popular areas and only 35 minutes drive from the city.
I have friends who live in Seaford Meadows. They had a house built 5 years ago and endured scumbag neighbours for 18 months before the house was sold again. They now have great neighbours. You get bogan housing trust renters, bogan owners and everyday bogan renters and they seem to come and go. You also get great renters so it's a real lottery.
Have you any contacts within the police force? A lot of British police were recruited and maybe someone can put you in touch with someone who can help. There are quite a few stationed at your nearest police station in Christies Beach. Maybe someone on here can help?