France and Germany are suffering the economic malaise of the Ukraine War, they will rebound when it ends. The UK benefits from North Sea oil, yet their is growing resentment. Hollyrood resents sending their tax money to the paper pushers at Westminster. Most of the gains within the UK's economy is in London while the rest of England rots.
Your first point about the economic malaise ending when the Ukraine War is over is very optimistic. The stagnation in Western Europe was firmly evident from 2016-2021(post-Brexit, pre-Ukraine). The empirical data strongly suggests that Western Europe has been on the wrong track since 2010.
If you pull out a crystal ball and start making prognostications about the future anything is possible. Of course, that's not empirical evidence. That's merely speculation grounded in your support for the European Union.
Your most fair comment is London's economic dominance relative to the rest of England. I don't want to revisit the reasons for the Brexit vote, but that summarizes the voter frustration with successive British governments and the EU.