Locomotive 9711, isn't equipped to haul tourist shuttles. It would only ever be used to haul truck shuttles.
The cars inside the train are shown to have crashed into each other and the train. However the trains are incapable to stopping violently enough to cause cars to smash through barriers, and cars are parked in gear with their handbrakes on.
The French tunnel Portal is far larger in real life. The portal was a film set, made to a reduced scale.
The overhead power lines (Catenary) are missing from the rail tunnels. The tunnel lighting, walkways and wall mounted pipes aren't quite true to life. The tunnels were sets.
When the soldier tells Jamila that the tunnel is closed. If you look to the far left of shot you can see actual tunnel customers joining the queue to cross - unhindered. The Eurotunnel were still operating during filming.
In the opening scene there is an establishing aerial shot captioned 'Folkestone, UK'. But the aerial shot actually shows Dover harbour.
The French army blow up the tunnel portals to prevent aliens from getting into France. However there is a large ventilation shaft about 3km from the tunnel portal, this would need to be destroyed to trap the aliens. However it clearly isn't as the children have just walked under it.
A British character makes reference to a tire iron when talking to another British character. British people would call it a wheel brace.