Alternate History: WWII Might have beens

Everyone agrees that Hitler's greatest mistake was to take on the Russians before finishing off the British. In 1940 the German army had shown it was lightyears ahead of every other army.  The Germans had occupied Denmark and Norway, invaded and conquered Poland, Holland, Belgium, and even France.  All the Germans needed to do, to settle Britain's hash, was to get their army, actually just a small part of their army, across the English Channel.  After Dunkirk the British Army was in no shape to stand off an invasion of Boy Scouts, let alone a couple of panzer divisions. 
   The only problem from the German point of view, was getting their army across the channel in one piece.  They had about 2000 Rhine river barges to make the crossing in.  These were seaworthy enough for a channel crossing in good weather.  Summer weather.  Trouble was, the British had a couple of hundred destroyers, fifty cruisers, and a dozen real battleships to oppose such a crossing.  When the British steam up along side a river barge in a destroyer,  that's the end of the river barge and all its troops, (or cargo).  The Germans only had about ten destroyers, some subs, a couple of cruisers, and a couple of light duty battleships.  The Royal Navy would have an enjoyable turkey shoot cleaning out that batch.   The only equalizer the Germans had was the Luftwaffe, and for that to be effective it had to defeat the Royal Air Force.  You cannot take out surface vessels when you have Hurricanes and Spitfires on your tail.  The Germans tried to take out the RAF in the summer of 1940, resulting in what we now call the Battle of Britain.  Unfortunately for Hitler,  the RAF out shot the Luftwaffe that summer. 
   One equalizer that the Germans might have obtained, the French Navy.  France was a great power, and had a sizable Navy, not quite as big as the Royal Navy, but far superior to what the Germans had in 1940.  The French were pissed off at the British, they blamed the British for their defeat by the Germans that summer.  According to the French, the British didn't send enough troops, enough aircraft, and they bugged out when the going got tough.  If the Germans had stroked the defeated French enough, they might have been able to get the French to join them in an invasion of England, and bring along their Navy.  This would have required a lot more diplomacy from the Germans than was usual for them, but it might have happened.  And if so, it would have been curtains for the Brits in 1940. 
This worried the British so much, that they sank a good portion of the French fleet in North Africa just to make sure they didn't join the Germans.