Unlike Napoleon, Germany would've defeated all the land powers in Europe. The Germans would make sure the French don't have a third round (and even then I doubt the mood in France would favor such a course of action) and a Brest-Litovsk style treaty cripples Russia and leaves it in no position to fight Germany. A victory in 1914 also means America doesn't even think about favoring the Brits too much.
This leavea Britain in a position where it can sustain a blockade of the North Sea (and even the Med at the risk of pissing off Italy and the Ottomans) for a while, but with nothing to look forward to.
They also can't keep this up forever. Spain and occupied France would serve as points to break the blockade, and America would mount pressure to lift the blockade to be able to trade freely with Europe. The Germans also have all a shit ton of industrial power and resources at their disposal, and they'll find some way to hurt the Brits. Securing Ottoman entry and a push towards Suez comes to mind, for example.
The British have no good prospects if they keep the war going. In all likelihood they would leverage their untouchable position to secure a peace treaty that deals with immediate security concerns, namely keeping France as well as possible and denying Germany channel ports.