Originally Posted by
Bing
The latter would have proved unlikely to show up for Sea Lion as she only started sea trials on 15 Sep 1940 with Tirpitz a few months behind. The other issue the RN faced with the Kriegsmarine was that they could be anywhere so concentrating enough assets in one place to neutralise even a U-boat was an enormous task, this wouldn't be the case if the invasion had gone ahead as you'd know exactly where they were going to be.
However what was most likely to cause the failure of the German invasion plans was lack of experience and equipment, even with the right equipment Dieppe was a disaster for the Allies, imagine doing it without proper landing craft.
You are quite right about Bismark, it would have been better to have used Scharnhorst and Gneisenau as examples. You're also right about the concentration of forces, but that is a double edged sword, and the RN's ASW capability wasn't particularly good at that stage of the War (as evidenced by the U-Boat's 'Happy Time'). Additionally, the RN would have been defending itself against air and maritime threats simultaneously, whilst trying to defeat a landing force.
Your Dieppe point is a good one, but the nature of the operation and the organisation of the defences would have been quite different. Again, the application of airpower would have been very important and, at Dieppe, the raid was undertaken in an unfavourable air environment, and different to that faced by a Nazi invasion of the UK had Fighter Command been defeated. That's not to say lack of experience and equipment would not have been an important factor; I don't think treating the planned landing as an extended assault river crossing operation was remotely sensible.