[kevf]

In the old cold war days I travelled from the Uk to Japan on the Trans-Siberian Express. Ferry to Holland, train to Moscow travelling through Germany and Poland, then a few days on the Trans-Siberian to the east coast of Russia. Last leg of the trip was a 2 day 'cruise' to Yokohama.
Your trip would be close to 10 days (assuming you did'nt stop over in places like Warsaw and Moscow), so you definately can't be in a rush to go this route. Some of the scenery is fantastic, but a lot of it is a bit boring, the thing that made that part of the trip special for me was the people that I met who were also travelling to Japan via this route.
I did a little bit of searching on the internet before i posted, it looks like its still a viable travel option for you if you have the time.