In reality, Rick Allen didn't leave the hospital to play with his re-attached left arm. The doctors removed it after only 24 hours, since other parts of his body were being infected. This scene was a dream.
During the "Photograph" writing scene, the Mutt Lange character is playing a Roland JX-8p. This synthesizer wasn't developed until 1984, a year after Def Leppard originally issued the Pyromania record.
It is shown that Zildjian Avedis and Z-Custom cymbals were used in the movie. Z-Customs were not around before 1986. The Avedis cymbals in the movie were shown to have Avedis written above the Zildjian logo. The new logo wasn't introduced until the 1990's.
It is shown that Zildjian Avedis and Z-Custom cymbals were used in the movie. Z-Customs were not around before 1986. The Avedis cymbals in the movie were shown to have Avedis written above the Zildjian logo. The new logo wasn't introduced until the 1990s.
In the scene where Joe Elliott is driving and listening to "Pour Some Sugar on Me" he reaches down to rewind the tape. Immediately before he reaches down he passes a white car parked on the side of the road. When the shot cuts back to Joe from the tape deck, he passes that same white car again.
When the guys are at Joe's house in the beginning he goes to get his "Deaf Leopard" poster and stuff that he drew. When he returns you see Pete Willis from behind reach out to take the poster in his hands. When the shot cuts to a front shot of Pete he is empty handed and takes the poster again.
When the band is recording "Bringin' on The Heartbreak", Mutt tells Joe to sing the hook in the chorus in a higher tone. Joe sings one line and Mutt tells him to stop. However, in the playback that follows, Joe's voice has been dubbed over and he has sang at least three lines in a higher tone.
During the opening scene the black corvette passes a road sign. The road sign states that the car is on the A57, 2 miles from the M25, 11miles from Sheffield and 46 miles from Manchester. The closest the M25 comes to Sheffield is about 170 miles.
When they are flying over London right after the American tour, we see a plane landing. The only problem is that it's a Boeing 727. It is unlikely any airliner would use this type of plane for a transatlantic flight. Reason number one is that it's a narrow bodied aircraft, reason number two, transatlantic flights accommodate large numbers of people, and therefore almost always use giant jetliners.
Shortly after Rick Allen's accident, the band can be seen in the studio laying down audio and practicing guitar riffs for "Pour Some Sugar on Me." Joe Elliot, Phil Collen, and other members of the band have stated quite publicly in numerous interviews that "Pour Some Sugar on Me" was the last track to be recorded, based off an improvised guitar riff, after the album was already considered finished. It was a last-minute add on that took two weeks to record, light years in Def Leppard time. Therefore, "Sugar" would not have been thought of or recorded until late '86, early '87, not 1985.
Just before they record their first song (Ride Into The Sun), their drummer quit. This was portrayed correctly. By the time they record the song, Rick Allen has been hired and is playing drums on the song. In reality, Rick Allen didn't join the band until after they recorded the EP. On the EP, the drums were actually played by and credited to Frank Noon, who played in The Next Band.
During the first U.S. tour scene, in 1980, when the newspaper stories are superimposed over the band playing, you can read the line "Put down your pens, children. We have a winner for album of the year!" Later in the movie, in 1983, after the release of "Pyromania", the boys are sitting in a bar reading the great reviews and Phil reads this very same line out loud.
Another detail that shows that this was filmed in the US, rather than the UK, is the power lines in many street scenes. British cities (of which Sheffield is the fourth largest) pretty much all use buried cables for power. Some places still have poles for phone wires (although not usually in the inner city areas) but leaving aside tram/train overhead wire systems, and rural areas, there are virtually no above-ground power wires in British towns and cities.