Okay, assume that Napoleon settles down after Tilsit. He doesn't invade Spain; Russia ends up coming to terms with the French hegemony over western Europe, although relations are... tense. Nobody can really break the continent.
I don't think Napoleon would be able to (he never did in OTL after all) shut out all British commerce from the continent. But he certainly can set up a tariff wall to discourage British trade.
Would Britain launch an earlier, more aggressive push to open up Japan and China? Keep Java?