When Harvey drives Ray to Florida to view the original film, the first shot of the front of the car shows a faulty headlamp on the right hand side. When the car draws into Harvey's drive this headlamp is now of normal brightness.
Whilst the autopsy is being shown on international television, Kiev is shown to be in Russia, when in fact Kiev is in the Ukraine.
In one scene, Harvey is seen playing a video game on the Nintendo Entertainment System, indicated by the fact that he is using an NES Zapper. When we see the game (which was made up for the movie), the game's graphics do not match up with the 8-bit limitations of the NES.
Early in the film, Santilli runs down the stairs in Nan's house, and when he reaches the bottom he grabs the stair rail. The whole thing moves, revealing this house to be just a set.
At 21min 33sec, Harvey's house has external security bars on the front windows. Only one of the three side windows has external security bars. The tracking camera shot at 1hr 15min 26sec confirms that there are no internal bars on three of the side windows.
When Gary is traveling on the bus, its exterior has an advert for the musical "Mamma Mia". However, if the film was set in 1995, "Mamma Mia" didn't open until 1999.
In a few scenes at the hotel by Heathrow Airport, several British Airways aircraft are seen, all with the current paint scheme instead of 1995's.
When Ray is delivering the pirated video tapes to his friend, in the background shots there is a Citroen Xsara Picasso quite visible in the scene. This is a car that was launched in 2000 so wouldn't have been on the streets of London in 1995.
In 1995 after the showing of the film at "The Museum of London" a crowd of photographers and news people rush Ray and Gary. One news cameraman is shooting with a Sony HDR-FX1. This High Definition video camera wasn't released until late 2004, almost 10 years later.
When Gary is traveling on the bus there is a shot of the bus in London traffic with a Ford Mondeo behind, this shape Mondeo was introduced in October 1996, the film is set in around April 1995.
During the filming of the autopsy, the "observer" starts messing around behind the window. If you look at the reflection you can see Ant has taken his helmet off during filming.