This doesn't look quite so bad now there are weeds (and the Gunnera) growing up around it. Still, corrugated iron ain't all that picturesque. Plan is to block the pipe, scratch a level foundation in the rotten rock below the outlet then lay the 20 odd concrete posts rescued from the other site as a catch to stop further erosion. They will be hidden with large chunks of rock I've been bringing in from the back of the farm (as will the end of the pipe). With luck and a few months it'll hopefully all look quite natural.