Biarritz to SJPD

There are several threads on this topic. A wide range of prices and early September is still part of the summer holiday season.

Biarritz is a lively and wonderful city with magnificent beaches and faded 19th century glamour. In the early 2000s it was a favourite destination for us as part of family camping tours of the Atlantic coast of France and Spain.
In the last couple of decades it has become a favourite second home for many wealthy Russians and other international jet-setters.
So I don't have any hotel recommendations for you, but Booking.com no doubt will, at a price!
Last summer, as part of a cycle tour we rented a nice self-catering cabin on a campsite in Bidart, just south of Biarritz. That was affordable and well connected by local buses/taxis and cycle lanes to the centre of the city.
The cafe at the Grand Casino is my tip for people and wave watching. And it has the most extraordinarily decorated art-deco restrooms too!
Enjoy your stay and Buen Camino for your walk!