It's awful. I feel so sorry for you. My neighbours weren't violent or loud - they were outwardly very respectable which meant that people believed them for a long while.
So much harassment from them in the form of lies to neighbours, the police and council, damage and petty theft, legal letters and a boundary dispute which dragged on for four years that they lost because it was completely unreasonable.
I'm glad we stayed and she fucked off but I felt under siege in my own home for four years. I would dread yet another fat legal letter landing on the mat. Even though I knew it was lies and felt sure we'd win it was so worrying. Plus, it cost us money to respond, but not as much as they wasted on it.
That was bad enough but I don't know what I'd do if they'd been thugs like your neighbours.
Probably move, I expect, but I understand how angry and frustrated you feel. We felt indignant at the idea that we should move. Why should she drive us out? We love it here.
We spent every day for four years talking about her. I lost half a stone during the three day court hearing. I can understand how marriages break up. Thank god we didn't have anything else serious to contend with because I think we'd have gone round the twist.
One thing I would say is do not be afraid of making a formal complaint in case you jeopardise a sale. If the sale's going to go through imminently, then bite your tongue, but these things sometimes do drag on and you might reach the stage where you have to say something to someone - the council, the police, your solicitor - especially if the people are threatening or abusive.
And you don't have to declare every dispute. If it's resolved, there's no need. Not saying you want to fight every battle but don't be afraid not to.
Good luck with whatever you decide