Sorry, I should have realized the route went through gauge changes, even though both ends are the same gauge. That's a pain. It's a routine operation, but a big one.

Not sure what they do about loading gauge. The UK has many limited loading gauge lines, due to old tunnels and bridges. No way will a double stack container train fit in the UK. Here's a brief world loading gauge summary.[1] The leftmost outline is the general UK limit; some lines have more clearance, especially the ones that connect to Eurotunnel. The next one is the general EU limit, small by world standards. Note the round top. AAR Plate B is the basic US limit; any Plate B boxcar can go on any US mainline track. 95% of US track accepts AAR Plate C, the "hi-cube" boxcar. AAR Plate H, 20' 3" high [2] is for double-stack container cars. Union Pacific and BNSF have upgraded to that level.

China and Russia go in for big loading gauges like the US, being big countries with long distances to cross. Watch for China lobbying the EU to upgrade for heavier freight.

[1] http://emdx.org/rail/Gabarit/ComparaisonGabaritsEuropenEtAAR... [2] http://www.icrr.net/plates.htm

The train goes to a yard off High Speed One (built to the standard European UIC GC gauge) rather than anywhere on the domestic network. It won't be double-stacked anyway, as the structure gauge through Europe is too small for that to be possible. It'll be single-stacked 9'6" boxes on standard wagons.