set up meeting with said neighbour, ask politely if you can meet to discuss the issue, calmly. If they do no agree to meet then drop them a note to say you could seeking legal redress, it can be expensive though, but surely they can see you have a valid grievance. You read so many of these types of disputes that escalate into out and out war, best to try and sort it out. Do you know them well, buy a bottle of wine, ask them to meet at pub, do something social, then perhaps you won't be going grrrr or reaching for the shotgun.