A bit hard to take any of that seriously. Both Hitler and Student must have realized that by the spring of 1941 the British defences had become very much stronger, both in absolute and in relative terms; for instance, by the end of 1940 Britain was producing about twice as many fighters per month as Germany.sitalkes wrote: “Then a discussion followed about the use of the 11th Air Corps in an invasion of Great Britain. In this respect I expressed my doubts about using the Corps directly on the South Coast, to form a bridgehead for the Army - the area immediately behind the coast was now covered with obstacles. These doubts were accepted by Hitler. I then proposed that, if it proved absolutely necessary to use the 11th Air Corps on the south coast, then airfields in the hinterland (25 to 35 miles distant from the coast) should be captured, and infantry divisions landed on them.
"Suddenly Hitler pointed to the waist of the Cornwall- Devon Peninsula, and drew a big circle on his map round Taunton and the Blackdown Hills, saying: ‘Your airborne troops could be used here as flank protection. This is a strong sector and, besides, this important defile must be opened.’ He then pointed to Plymouth and dwelt on the importance of this great harbour for the Germans and for the English. Now I could no longer follow his thought, and I asked at what points in the south coast the landing was to take place. But Hitler kept strictly to his order that operations were to be kept secret, and said: ‘I cannot tell you yet.’"
Naval forces were also much stronger than they had been eight months before, and in Oct.1940-March 1941 Britain produced over a thousand tanks, even if many of those went to the Middle East.
The Germans by contrast were not appreciably stronger than they had been the year before, as regards their amphibious warfare capabilities; they would have to assemble all those converted barges, freighters, sailing coasters and whatnot again. The production of purpose-built seagoing landing craft had barely begun; Marinefährprähme were not delivered before July_August 1941. A few Pionierlandungsboote 39 would have been available. So would a few more Siebel ferries, but not enough to make a difference.
And a landing west of Portsmouth seems a particularly hare-brained idea. In 1940 the Kriegsmarine had rejected a landing in Lyme Bay for several good reasons. For starters, where would the invasion fleet come from? Not from the ports originally foreseen from Rotterdam to Boulogne, that would be much to far away, certainly for the barge convoys moving at five knots.