And if Napoleon lands, the British are screwed.
I would debate this point, because Napoleon's invasion plans (the crossing the Channel part) were...well...stupid. His plans relied on a large amount of barges which would not have been towed across the Channel but essentially paddled - I don't think they were even oared IIRC - that would have made the crossing turn into frankly a giant mess. A number of his barges were really thin in a way that would have only been sea-worthy in the most quiet of crossings, I believe he also had plans for circular, shallow-draft barges to seat 50 plans which would have just been disastrous, and the essential result would have been thousands of men drifting off down the Channel to either wash up 50 miles away and get instantly captured, or possibly even wash out into the North Sea, and that's not to mention the literal probable hundreds of barges which would have capsized, drowning all aboard. Added onto that that it would have been a national imperative for the Royal Navy to interrupt the crossing, so they would have gone in for the attack on the French Navy anyway, suicidal or not, knowing that their Captains would've been court-marshalled for not doing so if Britain survived the invasion, and would probably have spent half their time doing everything they could do disperse the barges - firing broadsides at them, ramming barges, and generally sailing between them to force the French Navy to assist in dispersing them, while making the entire clump of invasion barges gradually break up, increasing the chances of extra barges drifting off to their ultimate doom. Oh, and just to make it all worse, IIRC I think Napoleon's plan was for them to cross at night...because, you know...the barges would have surely been far less prone to getting confused and sailing in the wrong directions when they couldn't see their target...
Oh, and then there's the 130,000 men of the British militia who would have fought alongside the regular army.
It could have succeeded, I'll grant you. But a lot of people think that Napoleon's problem was that he thought that a naval invasion could be organised with as much accuracy and control as a land movement of forces, and the result would have been him losing half his army to the sea crossing.