On a Saturday, 5/27, we want to go from San Sebastian to Paris. We will pick up the TGV in Hendaye.
Is a bus a reliable way to get to Hendaye or would it be better from a reliability standpoint to take a taxi? We want to catch the 9:45 am train leaving Hendaye that gets to Paris around 3:30 pm.
What is the best website to purchase this TGV train ticket from Hendaye to Paris?
This is a bit of a strange trip. Between San Sebastian and Hendaye, it appears that you could use a local train if you didn't need to leave Hendaye so early. The line used to be called "FEVE", but I believe there's a new name that I don't remember. In any case, the best I can tell, there is no train that will get you to Hendaye in time for the connection you want to use. The late-May schedule isn't available yet, but I wouldn't count on an additional train showing up.
Incidentally, I'm pretty sure that local train doesn't use the regular station in SS.
I think you're right that your best bet would be to take a bus. It appears that there are buses from SS to Hendaye, but I'm not sure how frequently they run, and particularly whether there are departures early enough on Saturday to work for you.
I did find schedules indicating frequent buses from SS to Irun, a town on the Spanish side of the border just across from Hendaye. I've linked to the E26 schedule, which unfortunately doesn't give the running time of the bus. ("Donostia" is the Basque form of "San Sebastian".) I'm not sure exactly where the bus would drop you in Irun, but if you zoom in on Google Maps you can see that it's not likely to be very far from the Hendaye train station--probably just 1 to 2 miles. A taxi shouldn't be exorbitant if you're not able to find a local bus of some sort.
I would expect the buses to be relatively reliable, subject to the usual vagaries of road traffic, but I would want a great deal of padding if headed for a pre-paid, non-refundable rail trip.
Should you decide it would be prudent to be closer to Hendaye the night before your train to Paris--since a last-minute replacement ticket would be very, very costly--I would suggest considering Hondarribia, assuming you can verify the availability of onward transportation to Hendaye. Hondarribia is a very, very nice town, well worth a visit in itself. It's close to Hendaye but lacks the direct bridge access that Irun has, so a taxi to Hendaye would surely cost more. There are frequent buses from SS to Hondarribia, taking about 40 to 70 minutes depending on the route.
I'd buy the TGV ticket on the SNCF website. Watch the URL in your browser to be sure you don't get shuffled off to raileurope.com, where you will almost certainly pay more for the ticket.