Goering fibs or exaggerates, saying he can provide aerial superiority over Operation Seelöwe. Thus, Sept 1940, the barges are amassed in France, and loaded with the allocated 26 infantry and panzer divisions, left their French ports and entered the English Channel. Luftwaffe air cover was provided, and a KM escort consisting of Scharnhorst (field repaired in June 1940), Admiral Scheer, Lutzow, Admiral Hipper, Prinz Eugen, Nurnberg, a dozen destroyers, 20 e-boats and 30 U-boats.
Britain knows they're coming and has been recalling her warships into ports across the south, and holding back her fighters (one reason Goering is so confident). When the Germans are almost mid-channel, they are met by the RN's battlecruiser squadron (Hood, Repulse, Renown), 30 cruisers, 85 destroyers, 20 submarines (and their Perisher qualified COs), along with dozens of FAA, Bomber Command and Coastal Command strike aircraft, under the cover of over 500 radar-vectored Spitfires, Hurricanes and Whirlwinds (4x20mm in the nose). Behind them, coming down the coast at 25 knots, are all five QE class battleships and further destroyers.
In short, it's a bloodbath. It's not one sided, and there are significant losses to the RN, but the Royal Navy has but one priority in its existence, beyond escort duties, flag waving or colonial protection, and that task is defence of the homeland from invasion. Thus there's no chance any RN ship with a man and a gun operational will let the Germans pass. In the end, every single invasion barge is destroyed, along with all but one or two KM destroyers and the smallest of the escorts. The Luftwaffe air cover is smashed. This one day surpasses the Siege of Luknow in 1857 as the greatest number of Victoria Crosses awarded in a single action.
So, what is the impact on the war of a foolish German attempted invasion as I describe? Surely Goering is shot, Raeder or KM brass likely arrested. But Hitler just lost 26 divisions of top soldiers and tanks, along with the KM's surface fleet and much of the Luftwaffe. How does Gobbels spin this one? Are the French willing to return to the fight? What of Norway, Greece and North Africa? Mussolini must be questioning himself, especially once Taranto is attacked by the FAA's carriers that November.