conservative

In an era of deglobalization as it appears we're entering, it's going to increase the cost of things and increase the pain of making and buying things. If that's an inevitability (and I'd accept that perhaps it isn't), then getting ahead of the curve will mean that when the effects of deglobalization are just starting to hurt others, the brits will be further along in the process, potentially giving them a competitive advantage. Globalization and deglobalization are both situations that had positive and negative elements. Globalization has definitely increased global wealth and helped us buy cheap stuff, but it's also helped create more inequality and made global labour a race to the bottom. This isn't the first or last cycle of globalization or deglobalization, so even if you'd prefer it not happen, if it's going to happen anyway I suspect it might be better to have the pain sooner so you can have the benefits sooner too.

I suppose deglobalization doesn't necessarily mean a total end of trade. For example, even during eras of deglobalization, countries tended to continue to trade with their immediate neighbors. One benefit of getting in on deglobalization earlier than others would be fostering those relationships with trading partners outside of the context of globalization early with commensurate benefits of being an early mover.

The European Union isn't a very old organization, only being about 50 years old. It's entirely possible for such an organization to collapse under the strain of future issues such as an expanded and more militaristic Russia, and multiple impending sovereign debt crises resulting in part from a long-term cyclic increase in the cost of debt. Greece had just one such crisis and it resulted in much conflict as a relatively healthy Germany took the lead in helping to deal with that. If multiple such crises occurred and perhaps if the core economies in Europe such as Germany were not as healthy. In such a situation, countries already established with other countries individually would definitely benefit compared to countries suddenly fighting to figure out how to deal with multiple major issues at once.

There have been a number of different eras where hegemony of a certain empire makes wars largely uneconomical for other players. The Roman Empire's biggest rival was itself, for example. While there are other factors at play, those could come and go but the world superpower putting its thumb on the scale has an outsized impact.

If trade were necessarily a panacaea that ended all war, then there wouldn't be a war in Ukraine right now. Instead, we're seeing the western world tearing itself apart trying to use tools that aren't as powerful as they act and it seems they're in the process they're creating a more multipolar world since other countries go "Ok, I'll buy if they don't".

It seems to me that there are interconnected but separate issues related to unifying countries for the purpose of mutual aid and dividing countries for the purpose of giving different ethnic, religious, or political groups autonomy to prevent civil conflict, and that's why my viewpoints seem to be contradictory. While in an era of increased global conflict you might want to maintain a larger union to have more resources to defend against attack, you also need to ensure that the global conflict isn't internal civil war or other conflicts so your unified country can properly deal with internal and external crises. We have historical examples like Yugoslavia which point to a dangers of maintaining large unions when there isn't the civic harmony to support such unions. Both are occurring right now, because the same holistic factors that lead to one also lead to the other.

Some obvious potential counterpoints to what I've said would be that you might not think that a cycle of deglobalization is occurring so one country deglobalizing while everyone else further globalizes would not necessarily lead to competitive advantage (particularly for an island nation with limited local resources) since all it would do is increase local prices, and I think there's arguments to be made both ways but the conclusions I've personally come to based on the way the world is right now is that we're deglobalizing; You could remain completely unconvinced that the hegemonic power of the American empire is the driving force of the past 70 years of relative peace, and while I could give more examples where this happened, the world is complex enough that we could both have good facts and good logic and still come to different conclusions; My argument about trade not necessarily being a panacaea is certainly a bit weak because although it is true I can come up with examples where trade did not stop conflict, we also have examples of longstanding relationships where trade helped with cultural exchange and other beneficial effects so it's entirely possible to disagree with good logic and true facts; and finally my viewpoint of the contradictory nature of larger countries and civil conflicts isn't the only view on the matter and there have been examples throughout history of multicultural unions that didn't have massive existential problems as a result, such as imperial China or imperial Rome. Again, it's a matter where looking at things from different viewpoints two people could come to quite different opinions using solid logic and true facts.