Not mainland, but we went to the Azores (the remotest you'll get in Europe I think) a couple of years back, and will definitely go again. I don't think there are any direct flights, so all in, it takes almost a day to get there, esp. if you go to one of the smaller islands. We rented a little farmhouse, and hardly saw anyone for 10 days. Sensational and unusual scenery, sub-tropical climate and absolutely nothing happening. Bliss.