OP approach the police and ask for the log of all incidents reported by you in relation to the ASB.
Ask your neighbour to do the same, so you get an idea of quite how many times they were called.
Then approach your council for Subject Access Request relating to the ASB. This should include meeting notes, actions to take, and what they were advised to do by the police.
Then, when you have the full info, go through it, painstakingly to identify any mistakes, any times the council workers or police didn't take it seriously and get legal advice.
I have my own experience. My druggy neighbour, in the middle of a cannabis induced psychotic episode decided he was my partner and climbed onto my balcony, entered my home and demanded sex. I fled, called police, demanded the council rehome him. They refuse. I pleaded, begging them, I was not safe in my own home. They ignored me. He started stalking me, knocking on my door at 3am, harassing me.
He called 999 saying I had locked him out (of my flat), police knocked at 3am demanding I let him in because I was locking him out of his home. They would not believe me when I said he didn't live here, was my neighbour, and was harrassing me.
I slept with a knife under my pillow for weeks.
I ended up emailing the tenancy office every single incident, every door knock, every stalking incident, and doing the same to the neighbourhood police.
Eventually, I had an apology from the police And the tenancy officer had him committed for a while.
He's been as quiet as a mouse since.