I've been reading (or more properly, listening, with the help of the ipod and a book on CD from the library, while going to the gym and such) The Duel: The Eighty-Day Struggle Between Churchill and Hitler by Joln Lukacs which is about the period in May through August 1940 when France fell, and as Hitler tried to decide whether to invade, bomb, or seek a treaty with Britain. It's a fascinating book, in part because it focuses on the period when it still seemed like the US might never enter the war, and when a considerable group of people in Britain supported making a treaty with Hitler which would cede him the continent while leaving Britain and her empire independent. Once the bombs started falling on Britain in August, Churchill's support became nearly unanimous.
One of the interesting things that is mentioned in the book, is a plan that was briefly floated in June of 1940, after Paris has already been taken, while the French government has fled south. General de Gaulle and others in the French and British governments developed a plan to declare France and Britain to be a single united Franco-British Empire. Citizens of each country would be automatically made citizens of the other, and the fleets and colonies of the two empires would be held in common.
The goal was to keep the French Empire in the war, even as it became clear that continental France would be conquered within weeks if not days. The proposal was put before Churchill, who after brief hesitation endorsed the idea and proposed it via phone to French Prime Minister Paul Reynaud. Churchill hoped that in addition to keeping French naval and colonial resources in the fight, that a show or solidarity between France and Britain would inspire the French to continue fighting rather than surrendering.
Reynaud liked the idea, but he was already on the brink of being toppled by Philippe Pétain, who led the faction which wanted to seek terms with the Germans. Unwittingly, Churchill's proposal gave Pétain what he needed to consolidate his power. Rather than a show of solidarity, Pétain and his supporters saw the suggestion as an attempt by the English to swallow France and make it a colony of England. He and his supporters believed they would retain more Independence by siding with Germany. Within days, Pétain formed a new government, which reached terms with Germany. de Gaulle escaped to Britain, where he became the leader of the Free French.