I'm sorry, but this is complete fantasy. For one thing, Warspite isn't going to be anywhere near the invasion area - no RN officer in their right mind would risk a warship against all those barges with improvised weapons on them. Even if Churchill did his usual trick of ordering them in anyway, there simply wouldn't be any ammunition to spare for shore bombardments.
While I agree that she would probably not be there, it has absolutely nothing to do with the risk from weapons on the barges which would not have discouraged attacks by Destroyers or smaller vessels, as these weapons would lack either adequate (or any) fire-control or a stable gunnery platform; she would not have been there because the government and military intended to continue the fight from the Dominions in the event that Britain fell and a battleship takes a lot longer than a destroyer to replace. Plus she would also almost certainly have been based too far away from the Channel to interfere in the initial crossing.
Also for a hypothetical bombardment of the hypothetical beachhead an "R" class would have been used as they were considered to be more expendable.
In this scenario they will quite naturally be concentrating their fire on the invasion fleet. Very likely Warspite wouldn't achieve anything even if she was there - it's been demonstrated quite clearly that the RN expended thousands of rounds for each hit they achieved, and battleships carried only a few hundred rounds of main gun ammo. If you include secondary batteries as well then I supppose it's possible she might get a few barges, but out of a total fleet of four thousand that's just a drop in the bucket. Frankly, I think she'd have all she could do just to defend herself from the Kriegsmarine escorts (the Luftwaffe or U-boats would probably finish her off).
This passage shows a fundamental lack of understanding of the difference in difficulty of hitting a barge carrying weapons unable to hurt you travelling at seven knots at most compared to hitting a ship carrying weapons that can hurt you travelling at 25 knots plus.
Or the understanding that many of the barges were in pairs being towed by tugs which actually improves your odds of impeding the invasion dramatically - hit and disable either the tug or the first of the two barges in the chain and all three of them are delayed temporarily to permanently.
Nor does it show an understanding of the effect of the Norwegian losses on the Kriegsmarine's capacity to support the invasion, or the relative availability of British Destroyers and other escorts compared to Kriegsmarine numbers.
Your numbers also sound like WWI numbers based on Dogger Bank and Jutland - fire control and shell quality had improved immensely since then. Can you point me at your source, please?
Had Warspite got into range of an invasion flotilla that flotilla would have been severely damaged and broken up or sunk.
Your suggestion about the Hurricanes is even more risible. The RAF will be fighting for its life against the Luftwaffe, AND trying to interdict the invasion fleet, AND trying to protect any RN ships futilely trying to do the same thing, AND stop the Luftwaffe bombing at will! I don't know how you imagine the RAF could operate successfully under those conditions - they might be able to do any one of those things, but not all four. Remember, the Luftwaffe is coming fresh off the heels of not one but two victorious air campaigns, in one of which (let me remind you) they BEAT the RAF elements committed to it! RAF morale will be poor, and if any Hurricanes make it to the area then Bf109-F models will completely outclass them. We can assume there will be some pilots who fight bravely, of course, but they'll be expending their ammunition in a desperate struggle against the superior Luftwaffe, not bringing it home! Any pilots with spare ammo on their way back will be cowards who aren't interested in fighting anyway, I can't see them risking their lives strafing infantry (who would have all those AA guns defending them anyway).
I think you should take a look at the Luftwaffe's success against surface ships in the period 1939-41, and how long it took them to form and train up the specialised formations they needed for the task. While the Luftwaffe had the required anti-ship capability late in 1941 and 1942 in the Mediterranean they did not have this capability in 1940 - not for a lack of aircraft but for a lack of training and doctrine.
The situation off Dunkirk in 1940 is not replicable to the Channel as a whole.
A lot of people have been talking about British land forces somehow defeating the invasion forces that land. I think this might be the craziest part of all - this is the German army we're talking about here! They defeated Western Europe in 6 weeks, including the best that the British army could throw at them! I don't think they're suddenly going to become competent. If you look at the details, it's quite possible they won't even make it to the invasion areas. Don't forget, the civilian population will panic as soon as they realise the German invasion is coming. With roads and railways blocked by hordes of fleeing refugees and civil order breaking down, the British will be unable to move troops or supplies (this is what happened in Western Europe, you'll note). And of course, the Germans are cunningly mounting their invasion during harvest time! This guarantees the most productive lands of South-Eastern England will not be harvested, making the British supply situation even more desperate.
With civil unrest, starvation, and the inability to move troops, the British will be forced to seek terms of surrender. I give them four weeks, tops, assuming the Germans haven't conquered the whole place already by then.
Regarding the food situation, Britain always imported a large proportion of her food and rationing had barely got started by the time a 1940 Sealion could be launched; there was still a lot of slack in the food supply compared to actual minimum need.
As for defeating the Germans? The Germans lack a significant quantity of armour and mechanised transport so no "Blitzkrieg" and thus no cascading civilian panic. And after 48 hours at most resupply becomes problematic to impossible; at which point fighting the British army, whatever it's quality, becomes impossible.
I just don't think you're taking this seriously.
I really think this phrase best applies to yourself.