I'm very honoured by the proposed addition of dear old 'astings as a city. Just off the top of my head, the only major ports in the south-east was/is in Dover and to a lesser extent Folkstone. Hastings has a beach-launched fishing fleet and a small, partially built, harbour arm, but it would be of only minor use to the German navy. The Germans could have landed on the shingle beaches or at flatter sandy beaches nearby at places like Camber Sands/Romney or Pevensey. Nearby Rye (a fellow
Cinque Port of Hastings) also had a small harbour. Basically what I'm getting at is that Dover & Folkstone should really be the only ports that can accept troop ships and all other coastal towns in the SE up to London & Portsmouth were only suitable for landing craft.
I've not been very active with Civ2 in the past few months since the data loss. I was gutted to lose my Sealion save just as I was consolidating my hold on London & preparing for the next phase of my offensive. I'd been very much enjoying the scenario up to that point, although I think that the initial invasion was slightly too easy (though a lot of careful planning did go into it). I think the main flaw was the speed at which I was able to reinforce the German bridgehead. If you can find a way of slowing down the flow of reinforcements (bearing in mind docks may well have been sabotaged or damaged) so that the Airborne and Amphibious forces really have to struggle to hold on for several turns against a British counter-attack, then I think the invasion would be perfect. I would also advise devising ways of beefing up the defences of London, perhaps with some pre-places bunker type units to represent the difficulties of fighting in a heavily urban environment.
I'm certainly not advocating for making the scenario massively more difficult across the board, but more for tweaking certain key battles to make it more of a 50/50 success/failure. Obviously, I didn't get the chance to sample the later British counter-attacks, but it seems to me the two most critical battles will be the crossing and London. Once well established ashore any competent player will be extremely difficult for the AI to push back into the sea with anything but massively ahistorical numbers.