Sounds to me like you really have two separate issues here - the PWA bit and the boundary encrouchment bit. Exactly what is the evidence that the boundary is incorrect. Do you dispute it or acknowledge it?
We are not disputing one post is over by about an inch. They say three inch, (so that show something about his manhood I think!) It was difficult to put in but it was ten years ago. we knew it wasn't straight about 6 years ago when we had a patio laid, but didn't know it was over, just thought it wasn't straight. the neighbour actually came round and helped put in a trellis panel next to it as we wanted to make sure it was in the right place, on our land. When he bought that one up yesterday, we said "you were there measuring it", he said "have you got the evidence"!! (actually I do know the day it was put in because it was at a time when we started writing down what was happening, as the woman of the house was having another verbal attack)
So worn down! We haven't once thrown personal insults at them but yesterday they insulted me my family and the way we choose to live and we feel this can not continue