I have just purchased France Rail 'n Drive passes from Rail Europe. It was all pretty straight forward ('though not necessarily EASY) I'm not sure to what extent they can help you, but you might check it out at http://www.raileurope.com Click on point to point tickets and enter your cities.

They will give you the cost of the tickets, and should also indicate the cost of the reservation which is $11 (USD) I don't know whether there is a problem with the one-way situation or not. You should be aware, by the way, that they/ you cannot make reservations for these trains more than 60 days before you want to travel. So, while I had completed my order, etc., in early March, I had to wait until April 13 for them to make the reser- vation and mail my tickets. (I wanted to travel on June 13.) I actually had to call them on April 20 because I had not received my tickets. They apologized, said they had been terribly busy, and made the reservation on the spot. The tickets were at my house two days later.

Altogether a pretty good experience, but I would recommend getting after them to complete your order if you don't have your tickets within 2-3 days of when they could reserve them.

Pat in California where it is less than 100 so far today...