[fennecfoxen]

Loading gauges might be a problem as well. Parts of the UK rail network are still on W6a, which means the clearance from tunnels and bridges and turns is too small to take standard containers on standard wagons: you need special low-deck wagons where the container sits down between the wheels (so there's extra space between the containers, where the rail bogies are). This isn't the most efficient way imaginable to move goods over long distances. The W10 standard (which allows the taller Hi-Cube containers for refrigerated goods and the like) is available only on a few corridors.

(Mind you, in the US, they use low-deck cars like this for about 70% of containers... the difference being that the US railways can double-stack the containers. It's a wonderful rail system.)