The closest part of France to the United Kingdom is Cap Gris-Nez in Nord in France. In July I did a driving holiday to France staying outside Calais in Guines. One of the places we did visit whilst we were there was Cap Gris-Nez. You can see England quite easily from the top of the cliff. There are quite a few footpaths around as well. The area was heavily fortified during the second world war and the remains of the various bunkers and fortification can be seen. Also there was the remains of a castle built by Henry VIII.