Re: I was more worried about the complete lack of people...
I, too, noticed the lack of people. Wasn't bothered by it, however: budget doesn't allow for unnecessary extras.
Still, with all the Underground entrance shots -- you'd think someone would have been shown exiting up the stairs, stopping, and looking around, scratching their head. Wouldn't have cost much.
Other, unrelated things:
Re: 'Merkins (I'm one of 'em) and the "Natural History" Museum:
The phrase would "trigger" (in modern head shrinker parlance) the ugly feud between the Evolutioners and the Creationists - BBCA does NOT want to get involved in that argument.
Re: Oxygen and "Airbag" effect
Perhaps the original (flawed) script made some mention of the oxygen floating up and re-enforcing the ozone layer (getting "activated" somehow by the incoming charged particles), thus providing additional protection from the solar flare / CME. Unfortunately, the word "ozone" is also a trigger, and might kick off an Eco-Green vs Filthy Polluters battle, so the word had to go.
In the BBC's quest for world TV domination by way of "dumbed down for the world" Doctor Who episodes, one lesson stand out clearly:
Never alienate _any_ demographic groups.
We see the results of this philosophy each week. Unfortunately.