It's a bit late in the period, but spare a thought for Venice? One of the mightiest trading hubs of the contemporary Mediterranean, highly defensible, and utterly beautiful.
It's like how in CoD Modern Warfare II the Russians somehow fly into the US on helos without ever mentioning the navy. Then as now, populist techno thriller writers didn't know their stuff.
Which is fine, because if they did they'd have a really bored audience.
Some of this thread sounds like the contemporary 'invasion fiction' people actually wrote in the early 20th century. The alliances there were no less ludicrous.
I'd argue that a British fallout would either be faux Edwardian (perceived as not as 'Dickensian' as the Victorian age, generally seen as the sun-drenched 'last gasp' of civilization before the lights went out in WWI; it even includes an arms race and invasion scares), or Agatha Christie time...
Impausibility levels of this timeline: intensifying. Not leas that the USA is recognizing (and implicitly backing) a state which wants to newly conquer an Empire larger than that of Alexander the Great.
Orwell later in his career was increasingly suffering from ill health and paranoia. If he lives into the '80s, then he is unlikely to be suffering from these problems until the very end.
Interesting, but I confess to being somewhat sceptical about how quickly these advances can be sustained with pre WWI logistics. I know that OTL's Eastern Front was pretty fast moving (for WWI), but getting to more or less the same place as OTL seems somewhat implausible. There are no tanks, no...