Out of work now. I'm going to add a bit on factions and mutants.

EDIT: Plenty of small mammals in England. Looks like Lurkers and Demons are also possible threats. Who would have known that the four major mutants in Moscow could be so widespread across the world? That said there are no wild wolves or bears, but as was said before foxes are an option, as well as a few species of deer and European Bison. Should pan out interestingly.

EDIT: Fun fact, deer can be omnivores. Prepare to see herds of mutated Muntjacs roaming the surface looking for tasty snacks.

UPDATE: Three new mutants completed, more to come. England has some good stuff to work with. Humaninals are unlikely to appear due to high levels of radiation, most likely something more drastic such as the librarians or blind ones will show up in certain places.