There was some mention in the extras provided on the DVD that the film makers of Edge of Tomorrow chose Normandy as the point of the battle, to hark back to WWII.
In WWII, the allies were using ships to deliver troops, and determined there were only two ports/points in the British facing coast that could support an oceanic invasion. They were Normandy and Cherbourg.
But the troops in Edge of Tomorrow were traveling in air transport. At first I thought it was very clever to trick the Mimics into thinking they were going to invade by sea, thereby concentrating the defenders fire-power about those two likely entry points, only to see them fly straight into one of the two strongholds!
Given France has around 2000 miles of coastline, and maybe three quarters of that is on the north-western side facing Britain, why not attack at somewhere else along that coastline, or indeed, set the entry point as '10 kilometers inland' and fly straight over the beach?
Beyond the psychological advantage of 'We beat the defending forces before at Normandy, so let's do it again!' (which I think is pretty weak) what was the advantage of attacking at Normandy?