About the prompt I don't think Napoleon would have been able to hold the British Isles in the long run or even if he could in the short term. But if he had he might have tried to get concessions from the British. Over what I'm not sure it would depend on his interests be they colonial or Continental, knowing him though probably Continental.
Probably not much different. He conquered much of the German States, yet the unified German empire was being proclaimed in Versailles palace by the victorious Prussian statesman goose-stepping their way through it in just 1870.
Napoleon, typical of all egocentrics, was incapable of keeping friends, and too good at making enemies, to have a lasting legacy.