It's often the simplest of things ...

yet also incredibly effective, was to put some opaque transfers on the bathroom windows. We got them while in the UK and they've really make the bathroom seem more of, well, a bathroom. The toilet is right beside the windows which overlook our neighbours garden and swimming pool. So, while a nice view from our side, it probably wouldn't be if looking up from a deck chair from their side! We still have a great view up to the hills behind the village and the, almost always, blue sky.