The violence we see on screen isnt about fertility, but the refugee crisis, and how poorly its managed.
We never hear from an actual authority figure about the governments attempts to solve the fertility crisis. If an infertility crisis of this magnitude happened, ethics and funding would cease to be road blocks. The chances of solving the issue goes higher, but so does the types of atrocities committed.
The main characters are all 3rd party groups and not in the know of official science operations, and carrying out their actions mostly for political reasons.
As sort of a metaphor for the rest of the movie: we see the military fighting with rebels. Despite being in the presence of a baby, the military itself, never thinks to provide an armed escort team to get the mother someplace safe. Mainly, because they dont have orders to. Why? Because once again, the fighting isnt because of the infertility crisis, it's about the civil unrest and terrorist organizations.
Since the government doesnt appear to have an official stance on the fertility issue, and the probability they at least got test tube babies created, it becomes a we can neither confirm nor deny type of situation.
- It was possible that the British government uses the "Britain stands alone" line to say that it was the only surviving nation left.
- Supported implicitly in the movie. The youngest person on Earth was an Argentinian who was killed (ostensibly by accident) while leaving a club in Buenos Aires. Doesn't sound like an anarchy to me. The idea seems to be that there are functioning governments, but they are a minority among those that collapsed.
- If Britain wasn't an attractive place to live the refugees wouldn't be trying so hard to get in, so that supports the assertion that at least mainland Europe is in big trouble.
- Theo passes by the Argentinian embassy just before he is kidnapped by the Fishes, it has flowers laid in front of it, so someone in Argentina is sending out ambassadors to other countries, or at least it's still a symbol of Argentina to people in London.