Firstly:

That scene when Ethan is on Le Shuttle and has fallen over the side, with another train coming the other way-he swings himself up just in time to avoid certain death. Which would never actually happen, as the trains in the Chunnel never pass each other side by side- there are in fact three tunnels, one for trains going to France, another for those entering Britain, and a third service tunnel.

Secondly:

The impression of the preceding scenes is that the train is going through the British countryside incredibly (or should I type ridiculously?) fast, i.e. as fast as the TGV. Which, as any British rail user knows, would never happen. Fast and the British rail network would never be used in the same sentence-apart for ridicule, or the phrase 'The state of the British Rail network is going downhill fast', and of course, this sentence.

Thirdly:

The train left on time/was not cancelled due to floods, strikes, staff shortages, privatisation, tragic train crashes.

Forthly:

No speed restrictions meaning that the train goes irritatingly slowly-e.g. 20mph when it should be over 70mph, or stopping at seemingly random moments.

Finally:

The train is mainly full. Which rail companies would love, but of course, post-Southall rail crash, (and of course, more recently, post Hatfield rail crash), everyone is far too scared to use the trains. They would fly...only of course there is the risk of DVTs.....Realistically, the train should be at least one third full, with a few empty carriages here and there.