I agree with mspath. Purchasing your ticket at the Bayonne station is simple and fast. It is a small station and the people who work there are friendly. Assuming you are staying overnight in Bayonne, you can buy your ticket the day before your planned journey to SJPdP. I'm curious about the the early pre-dawn departure time (0641). Assuming (lot of assumptions here) you will be staying overnight in SJPdP, you will be arriving there at around 0800. This will be way too early to check into your auberge. If your schedule permits, give some thought to staying a couple of days in Bayonne. I got over my jet lag here before going on to St. Jean. It is an interesting Basque city with a lot of history, and perfect for getting pre-Camino jitters under control. Bon chance!
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