Wirral County are mentioned as being the less successful rivals of Chester City, and despite the efforts of a corrupt chief executive, narrowly survive the 2007—08 season at the expense of Mansfield Town. In real-life, Chester City survived the same season also at the expense of Mansfield Town... only to get relegated the following year, before going out of business altogether in 2010 thanks to the actions of their corrupt owner. If you assume that the series' talent for predicting the future works both ways, then Mike only succeeded in postponing the demise of Wirral County by two years.
In the film, Scotland receive much mockery for their habit of getting to World Cups and then going out in the first round. In real-life, not only did Scotland not qualify for the 2002 World Cup, they haven't even come close to qualifying for a major international tournament since then, and most of their fans would probably be glad to go back to the days of actually getting to tournaments even if they don't make any progress there.
The England physio is depicted as being a pervert who insists on inspecting the players' groins even when the injury is clearly somewhere else, and in a deleted scene talks gleefully at length about how his job involves "rubbing young men's thighs." This takes on a much darker tone following the revelations in 2016 about sexual abuse of young players having been a serious problem in English football around the time the film was made (and going back several decades).
In England Manager, England progress through the group stages of the 2002 World Cup thanks to a controversial 1-0 win over Argentina, then progress to the semi-finals where they get knocked out by Brazil, who go on to win the World Cup. All of this actually happened (albeit with England's elimination by Brazil occurring in the quarter-finals) in the real 2002 World Cup, which took place a year after the film's release.
Then in Manager, Mansfield Town get relegated from the Football League at the end of the 2007—08 season. Guess what happened in the actual 2007—08 season?
Rufus Smalls in the film was mentioned as being an extremely popular striker whose reputation went down the tubes after he skied a penalty in a penalty shoot-out in the quarter-finals of the European Championships against Portugal. Fast forward to 2004, and David Beckham's reputation takes a major (albeit fairly short lasting) knock when he has a critical penalty against Portugal in the quarter-finals of the European Championships, and kicked it into Row Z.
We find out that Bassett lasted one year after the film as England Manager, after failing to qualify for Euro 2004. England failed to qualify for the real life Euro 2008, cutting short the career of manager Steve McClaren after just a year. Moreover, Bassett got Newcastle United relegated after managing England, which McClaren also proceeded to do.
Averted in one sense when the actual next World Cup to take place in Brazil rolled around in 2014; England completely bombed at the tournament and went out in the first round, the only thing in common with Bassett's team being that one of the results was a turgid 0-0 draw. Played straight in another, very odd sense however; in the film, Alan Massey taunts the Scotland squad by saying "Costa Rica are looking tasty this year." At the 2014 World Cup, Costa Rica proved to be the dark horses of the tournament, getting through to the quarter-finals and beating several more fancied teams in the process.
The David Beckham parody in England Manager is named Steve Harper. The Beckhams later had a daughter and named her Harper.
Unintentional Period Piece: England Manager can appear somewhat dated to modern audiences, as a result of the film quality, the footballers parodied (nearly all of whom had retired by the early-mid 2010s), plus the storyline being a very specific parody of the circumstances surrounding Kevin Keegan's resignation as England manager in 2000. It's less of a problem for Manager, oddly enough, which mostly references and parodies footballers from several decades before the series was made.