Interesting thread. Our neighbours bult up to the boundary. We weren't overjoyed because our own house is only about 75cm from it. They didn't think about overhangs etc but say taht they decided to build the wall on the inner line of the foundation (which was all on their land) to deal with it. When I went to put the fencing back up, it was pretty clear that the back corner of their extension veered over the boundary. God knows how - my guess is that their house wasn't square to the boundary. They insisted that the boundary must have curved to accommodate their extension because it was on their land. Thick as pigshit really, but we are talking about 15cm-20cm here or there. So I let it go, and put a slight kink in the fencing. Which was fine, until I realised it meant that I could no longer get a micro digger down that side of the house.

Oh well. Not worth falling out with them over it, we are both planning to be here for decades. But the lesson I learned is - never let them take down the fence in the first place. That way there can be no doubt.