In reply to ohsmeg:
If you going on the train, I wouldn't bother with a box. They are a grand imperial PITA - you've got to take your bike to pieces to some extent and it's something that I only do when the bike has to go on an aeroplane.
There is also the not inconsiderable problem of where on earth you think you're going to put a bike box on a train these days. If you must, just get a cover