Not sure if this is the right place to put this so apologies in advance.
Background- Semi-detached house, my conservatory is attached to neighbours extension.
Our neighbour recently replaced their fence. In order to fit the last panel they removed some of the guttering on their extension. The guttering was then replaced save for the downward pipe to the drain in their garden. The old pipe was a dog leg which ran down the boundary of their extension to the top of the fence, turning into their garden and continuing down. The replacement fence is a lot higher than the old shoulder height one and due to the new design, is slightly further into their garden (by about 5-10cm).
We don't have any issues with the fence.
The problem is they claim they now can't fit a downward pipe due to the new fence so the guttering just drains into straight over into my garden. This is causing absolute carnage. All the rain water from their house roof and extension roof now drains exclusively into the flower borders in my garden. Given the recent down pours the soil has turned to mud and due to the height the water is falling from, is causing an absolute mess (not to mention the loss of some of my veggies as they were essentially water eroded out of the soil). My conservatory looks like it's been mountain biking!
Surely this can't be allowed? I asked if the drain could be moved to the opposite side of the roof but they've just shrugged and said they can't do anything. They're not the best to talk with (due to previous arguments about over hanging branches from their tree) so I don't really know where I go from here.
My guttering goes straight down into the drain as did theirs so I don't understand why this isn't a solvable issue.
I'm concerned that come winter I'll have a water logged garden or worse, flooding in the conservatory. Any advice?