Most scenes were shot in Northern England.
Gary Hook was originally intended to be from Lancashire. At Jack O'Connell's request, the script was rewritten so the character came from his birthplace of Derby, Derbyshire.
Heavy metal band 'Derision' filmed their music video 'Predation' at Liverpool Newsham Park Hospital a few weeks after filming wrapped for '71. The abandoned hospital was used as a fictional barracks. When the band and crew arrived they discovered the set from the film still intact complete with sand bags and barbwire. As the music video was Zombie themed it fit perfectly, and the set from '71 appears in the opening scenes of the music video.
Sheffield's Park Hill Flats (empty at the time of filming) was used as a location to recreate the Divis Flats, a republican stronghold that stood at the bottom of the Falls Road, Belfast.