Going back to the Battle of Britain you have to remember that the UK was already out producing Germany in fighters (Spitfires and Hurricanes). Even if the Germans continued to focus all their attention on the Southern airfields the RAF would have built up reserves in the North. The more critical factor was trained pilot's, Germany would have had to have killed RAF aircrew in large numbers to truly deprive them of a credible counter to a seaborne invasion. The RN, regardless of the RAF, would also have decimated any attempted landing with the huge advantage in home fleet destroyers guarding the English Channel.
The fact that the UK had also completely compromised the German Abwher meant that any invasion fleet would have been detected as soon as it began to muster outside French ports. The Germans may have been able to sink a large proportion of the RN's attacking destroyers, but once the latter were amongst the invasion barges they would have caused havoc and huge loss of life.
Hitlers only hope of bringing the UK to its knees was blockade and a total U-Boat victory against the merchant marine lifeline from the US.
The fact that the UK had also completely compromised the German Abwher meant that any invasion fleet would have been detected as soon as it began to muster outside French ports. The Germans may have been able to sink a large proportion of the RN's attacking destroyers, but once the latter were amongst the invasion barges they would have caused havoc and huge loss of life.
Hitlers only hope of bringing the UK to its knees was blockade and a total U-Boat victory against the merchant marine lifeline from the US.