Sorry to hear about your neighbours, obviously your life style and opinions of what is normal is not shared by them, it is a fact that some people live like dossers and have a different understanding of what clean and presentable actually is ,
You are obviously getting aggrevated by it and this in itself is winding you up, just chill out a little look at it rationally , if you do start court proceedings/action this will gain nothing because when you sell you will have to declare problems with the neighbours and this in itself could put off potential buyers ....... just accept what they do or move on to put it bluntly, I know its not fair but life is not fair .....