New Year's Day a public holiday in France?

January 1 is a public holiday in France. The Sunday schedule is generally used for transport. If you are flying to Biarritz you can take a bus from the airport to the Bayonne railroad station /Bayonne Gare SNCF where you should be able to get a local TER train to SJPdP which leaves at 21:10.

You can take MSPATH's comment to the bank... Plan on it, as she says...

But, if you do not arrive at SJPdP until nearly 23:00, you BETTER have a hotel reservation and advise them of your very late arrival. The hotels there are generally small places and do not have 24 hour desk service.

A viable Plan B IMHO is to get from the Biarritz airport to Bayonne, and reserve a room there for the first night. There are several nice places near the train station.

Also, there are discussions of where to stay at Bayonne in the Forum. Just search on "Bayonne hotel, accommodation, or lodging."

You would take the morning train to SJPdP. I recall there are maybe five trains each day in that direction.

I hope this helps.

Stephen,

Great idea! There will be a TER line 62 train to SJPdP at 07:42 on Tuesday, January 2.

Have a good rest in Bayonne, Happy 2018 and Buen Camino!