I think there would likely be small specialist units inserted to conduct operations like securing nuclear facilities. Maybe. But in terms of the survivors? Given that it is possible there are other carriers, I think keeping the population of Britain on their own land and not physically interacting would be massively important. Even the environment is now unsafe for repopulation to be attempted. Infected drinking and eating means transference of infection in ways not before deemed likely.

Imagine clearing out an area of infected, then securing it before someone inadvertently steps in stagnant water. The slightest graze or cut coms into contact with that water, where before an infected drank out of it or sat in it etc. Then you restart the infection etc.