Having read all the thread posts, and having spent several weeks over a few recent years travelling as a research tourist between, and sleeping in Irun/Hendaye, I would recommend taking a taxi between Irun and Hendaye. Especially if you're arriving at Irun after long, international travel.
Yes there are regular train/bus connections between the two train stations, no it's not "very" far between Irun and Hendaye; but it ain't a 10 minute walk either.
If I had a choice at the beginning of such an adventure between (1)figuring out the unfamiliar, but short, train/bus connections between the two cross-border/international towns after a long flight, and then making those connections; or (2) walking across the border/bridge for +/-45 minutes between Irun/Hendaye stations; or (3) taking a taxi ---for +/-15Euros, I'll take a taxi.
Once at Gare Hendaye it's an easy train/bus ride to Gare Bayonne from where you catch the train to SJPdP and the beginning of your Camino. If you're late at Bayonne for the last train/bus to SJPdP, stay at the Monte Carlo Hotel just across from Gare Bayonne where you'll get a bed/decent meal for good prices and take the SJPdP train the next morning.