Rail europe has basic maps of train routes. There are some that you can travel overnight in a reclining chair or sleeper. They also have across europe train passes. We had looked into it ourselves, but decided that it would be too long and expensive compared to the cheap flights, and not easy as you get further south. Good luck though, would be interested to know how you get on. We travelled over by ferry to santander and then by road with a van last week, took about 35hrs in all. This was ok.
Anne