It's well known that military types create these plans against unlikely enemies because it's

1. Part of the job description
   
2. Potentially useful for war gaming in other contexts

So I wouldn't be remotely surprised to find that the UK's MOD has a plan to deal with a militarily hostile Europe. I'd be more surprised if it's a very detailed plan. But I don't think it's unlikely the possibility has been discussed and gamed out, if only to a basic extent.

That's completely different to the political doctrine which currently has the largely fictional Al Qaeda as Enemy of Democracy Number 1, with a present and active threat in Afghanistan.

Political doctrine is never debated. It's stated and propagandised, and it's purely for internal consumption. The real ends - which remain mysterious in Afghanistan, although personally I suspect opium and other drugs - are never stated publicly.

Which means that civil war won't happen in Europe unless it's useful and profitable to someone.

Just as the Nazis happened in Germany precisely because they appeared useful and profitable.

I'm finding it hard to imagine Catalonian independence - or its absence - being useful or profitable to anyone.

Likewise in Greece, which is an economic sideshow.

I can imagine the current crop of mad rulers breaking Greece just to prove they can, and for fun, with the possibility of useful profit, somewhat tangentially.

But actual civil war would surely spook the markets almost as much as a default would.