Its strange for me, I never play the Sealion Card. Why? Several reasons...
I'm not ever comfortable, in any game, with the way that the British Mainland invasion is simulated. No one quite knows how it would have come off, but it is a conceit to think it could have worked anyway as a feasible 'alt history' as in reality the Germans needed air and sea supremacy before the landings even had a prayer. At Sea they didn't even come close, in the air, it was very close but in the end a total failure on both fronts and they abandoned it. I like my share of 'what if?' fantasy and fully support the option to play Sealion, as would be a fantasy Invasion of the US mainland etc, but for me it is so 'off the reality chart' I can't get immersed in a German campaign that uses Sealion.
I am intrigued however to see if the Devs have grasped just how difficult it would have been in the Britain of the 40's to conduct a land invasion driving north. Britain is narrow, bounded by seas and mountains running north-south on the west side, then east-west when you hit the North. The major rivers run West to east, many are wide and virtually slice up the country into east-west segments. Rivers like the Thames, Severn, Wye, Great Ouse, Trent, Ouse, Tyne, Wear and Tweed are very large, deep and wide bodies of water, in the 40's there were far fewer bridges and many more fords and ferries creating controllable bottlenecks if the invasion proceeded primarily by ground assault.
A densely populated country, resistance would have been fierce; not only from the Armed forces, but from the militias. The so called and much maligned 'dad's army' wouldn't have been so much of a joke today had they been called into action. Every town and village had a trap laid. Every bridge, ford, crossroad, street intersection was booby-trapped and pill-boxed into a devastating ambush crossfire. What is chilling, if you research the Home Guard is that they were in reality suicide squads. There job was to ambush, harry, slow down, deplete, but at every ambush point they were expected, in the end, to be killed. https://www.iwm.org.uk/history/the-real-dads-army
That said, defeating Russia and getting a decisive win without undertaking Sealion, so holding off the Allies completely, is eluding me. Even on my best efforts where I take Stalingrad, Moscow and St. Petersburg and most of the Middle East, eventually I get ground down. I may have to treat SC as a 'game' not a historical sim and try it just to get the victory I'm after. We'll see..