Great Britain is not an Island

[Furunculus]

I don't know why you keep bringing this on. After WW2, Germany was in no position to threaten France in any way. Partitioned, no army, no economy, no political influence, not to mention that a little later France became a nuclear power. Since Germany wasn't (and still isn't and won't be), no military threat to France from Germany exists.

Granted, UK is somewhat different to most European states in that regard and London is still one of the world's top financial centers, but is going to change and importance of London as a financial center is going to decline. By using "channels" (I'm sure there's a better word, but nothing comes to mind right now) from the times of the empire, London still controls a good chunk of money flow from southeast Asia and Middle East and that is going to change in favour of new financial centers that are emerging there... I expect that in several decades, UK will adopt the Euro and start integrating more in EU. Maybe even earlier, it depends on a huge number of factors...

because france had feared germany for the previous 100 years as a result of the demographic slide of former relative to latter, of which the last grasp for dominance by france was the franco-prussian war. one does not cast aside a hundred years of decline especially after two world wars have just been fought on your front lawn. wiki ssums the situation up nicely (quoted below).

Britain is a financial hub for more reasons than just history, though that plays a large part. Not so long ago that position was occupied by New York, which goes to show how important the regulatory environment is. this along with that history, the ease of movement of people, language, culture and institutions all play their part.
Yes Britain will decline, all of the old west is declining relative to the 'new' east, and we will certainly decline all the faster if we integrate our financial sector regulation with that of europe.
You might be right about the timeline, I for one won't put any certainty on predictions cast decades into the future.