At the end of the movie, there's a written line claiming that Simon faced "strong criticism" from the climbing community after his return to England. This claim has been repeated in several press statements and reviews, but it's not correct. What really happened is that, one month after his return in Europe, Simon went climbing in the Alps, unaware that the Daily Mail newspaper had published a wildly incorrect version of the Siula story, implying that Simon had tried to kill Joe. This was of course absurd, and the British climbing community dismissed it immediately as nonsense. However, back home Simon discovered that a small group of senior members of the Mount Everest Foundation (the body that manages founding for climbing expeditions in the Greater Ranges) had misjudged the story and now wanted Simon excluded in the future from the MEF funds - a move that could basically kill Simon's climbing career. At this point however, Joe Simpson had a correct version of the Siula story published in a respected climbing magazine, and the whole issue was cleared. However, in the DVD commentary, Joe Simpson himself clearly says that Simon came under much criticism after returning home, and that he wrote Touching the Void to defend Simon.
Some of the long distance shots of Simon and Joe climbing the mountain are played not by the lead actors, but by body doubles, who were Simon Yates and Joe Simpson themselves.
The film makers took both Joe and Simon back to Peru to shoot on the actual glacier and terrain where the events originally took place. Local mountaineers were filmed on the glacier, but did not climb the actual mountain on Joe and Simon's request as they felt it was too dangerous.
The production spent a month in Peru but only 2 weeks of that actually shooting. The rest of the time was spent traveling to the remote locations. As Peru proved such a difficult place to shoot, they decided to only film what couldn't be filmed elsewhere and, once that was in the can, they decamped to the Alps where the transport infrastructure was much better.