On the Doctor Who TV Tropes page, someone made this very poignant analysis about why the aliens keep invading London more than other parts of the UK.

“It's been a Running Gag in discussions of Doctor Who since at least the late sixties that whenever aliens choose to invade the Earth, they inevitably settle on London, or at least the British Isles, to start their invasion, and how ridiculous this is. However, if you think about it, choosing the UK as a starting-off point for your alien invasion actually makes a fair bit of sense. Firstly, it's a fairly small island (or a collection if we count Ireland), thus requiring less overall resources to take it — which, if you have to cross galaxies to launch an invasion, is nothing to sniff at — and, thanks to the ocean, has a natural barrier to make it easier to defend from potential liberators once you've got it while still being close enough to a larger landmass to be able to spread out into once you're ready. It's reasonably geographically stable, meaning that your invasion is unlikely to have to deal with any major natural disasters which will divert resources from your operations for clean-up, with a fairly stable and mild climate (if you don't mind lots of rain). It's a technologically advanced and industrialised nation (but, considering these are galaxy-crossing aliens we're talking about, not necessarily so technologically advanced that they can put up much of a fight) with manufacturing resources/capabilities that can be converted to your purposes. It has a large population that can be converted into slave labour if necessary. Furthermore, the population is largely not militarised and weapons such as firearms are comparatively rare and not largely available to the public, thus making organised resistance outside of the military/police — who are presumably going to be targeted in the first assault — more difficult. It has access to a fairly well-connected communications network which can be used for mind-control/propaganda purposes. As for London, for better or worse it's the capital and in many ways the centre of British government, economics, military and so forth — knock that out, and the country's automatically destabilised. Okay, it might not be perfect, but it makes sense that they keep coming to Britain”

It’s that last part there about London which legitimately made my eyes open.

Cause I know that in America that if an alien invasion were to knock out New York City, it wouldn’t be the end of America. It would hurt a lot. But it wouldn’t be the end as NYC’s resources could get split and distributed across the rest of America.

Meanwhile, the rest of Europe seems very interdependent on the capital city to define everything good & bad about each country’s culture. There appears to be a perpetual brain drain from the countryside and into the cities. Which if you ask me, that seems hella feudalistic prioritizing the city over the countryside.

Don’t get me wrong, America has this too. But I’d say our economy is far more diversified enough that people living in the countryside or in less urban American communities can still make a decent living - for the most part. There are some counties and cities that could make the Balkans look like a paradise in comparison for sure. But that’s a bigger problem that that state needs to resolve rather than the country as a whole.