Children of Men (2006) by Alfonso Cuarón is a fable of a near future terrifyingly recognizable. An event (whatever it is), triggered a global situation of extremism in UK developing a tremendous policy of suppression, oppression and expulsion of every immigrant of the kingdom. Thanks to a state of emergency. the government owns the three powers (legislative, executive and judiciary) and applies a totalitarian policy for the sake of an elite.
One element of this policy is the creation of transit-towns where immigrants and offenders are brought to be expulsed by boat (as far as the film shows, probably a very long time after having being brought there). The processes of entrance of this heterotopia are obviously very clear (see the two following pictures) and life within those towns are shared between chaotic self-management and violent military interventions.
The story is supposed to take scene in 2027 but the universe shown by Children of Men is based on twenty years of democratic and economic regression, introducing a world very similar from the one we know. This feeling is achieved by using in its phisicality only recognizable elements which allows the comparison with nowadays society.