How is the story "The Destructors" restricted in terms of settings?

I find it interesting that you describe the setting as
"restricted" in your question. In my opinion, the setting in this excellent short story
is anything but, except if you mean geographically. It is worth seriously examining the
setting of this excellent short story and in particular how the setting contributes to
the atmosphere. Greene is a master of description and this short story is no exception.
Let us consider the setting as described at the beginning of the
story:

The
gang met every morning in an impromptu car-park, the site of the last bomb of the first
blitz. On one side of the car-park leaned the first occupied house, number 3, of the
shattered Northwood Terrace - literally leaned, for it had suffered from the blast of
the bomb and the side walls were supported on wooden struts. A smaller bomb and some
incendiaries had fallen beyond, so that the house stuck up like a jagged tooth and
carried on the further wall relics of its neighbour, a dado, the remains of a
fireplace.

Clearly, the
centre of the gang's world is a place of destruction. Descriptions such as "jagged
tooth" to describe Old Misery's house clearly paint an image of the horrors of war, and
we are forced to compare the setting to the beaten face of a human, with only one tooth
left in his mouth. Cars parked where houses once stood creates a bleak atmosphere,
symbolising moral desolation. This desolation is thus further developed and
characterised in the figures of the boys, and especially of course in T., who is shown
to express complete nihilism.

So, restricted it may be in
terms of scope, but the narrow geographical focus on the bomb site only serves to
strengthen the theme of the lives that the boys in the gang are living and how morally
they are a bomb site as well.