Short-story or novella version of Roadside Picnic?

In my copy of the novel there is an extensive afterword written by Boris Strugatsky where the story of writing the novel is explained. In that afterword there are at least two versions:

• A version published 1980 anthology Unintended Meetings which is described by the author as "disfigured, massacred, and pathetic" and the result of eight years of "battle" with the publisher and "two hundred degrading corrections to the text" an so on.
• The novel version (copyright date 1972), "completely restored and returned to the authors' version.

I don't believe the location of the zone is ever definitively disclosed.

As an aside, there is also a 1979 film Stalker with a screenplay written by Boris and Arkady Strugatsky, loosely based on the 1972 novel.

Futretrack 5 by Robert Westall

A fantasy of the near future in which Britain is divided into Zones and castes to which men and women are pitilessly allocated at the end of their schooling. Whether crazed proles in the Unnem zones, smug pampered bourgeois Ests or arrogant Techs, all are ultimately pawns of the computer that governs it all. One boy penetrates the conspiracy by which the nation is governed and has the knowhow to strike at the heart of evil.

What matches:

• Set in (future, dystopian) UK.
• Unemployed masses herded into Zones.
• protagonist goes "on the razzle" into one of the Zones.
• country patrolled by psychopters, equipped with psycho-radar that can detect criminal thoughts.