Pamplona to zubiri

Going by Rome to Rio the only option is a taxi(£22 to £27) No mention of a bus)
Others may have more knowledge
Woody

It is out of season so the bus schedules won't show up. Better to try close to the date. I'm pretty sure the ALSA bus from Pamplona to Roncesvalles would pass through Zubiri, and there is also a local bus company I think.

Autocarres Artieda has year round Pamplona to Roncesvalles bus service once daily on Mondays through Saturdays but no Sunday or holiday service. It stops in Zubiri. According to their schedule (horario) the bus leaves the main bus station in Pamplona at 13:50 weekdays and 16:00 on Saturdays.

autocaresartieda.com

According to ALSA/CONDA's website besides Pamplona and Saint Jean Pied de Port its bus also has these stops in Navarra: Zubiri, Espinal, Burguete, Roncesvalles, and Valcarlos. However, ALSA does not have a license to transport passengers between points in Navarra. That means that you can get a ticket to travel to SJPdP from each of those towns in Navarra but only to SJPdP.

So from Pamplona, officially you are not supposed be dropped off in Navarra. I suppose the driver can't stop you from getting off earlier than SJPdP but there are two cautions I can give you. If the driver doesn't see anyone to pickup in town he may not stop and if you are planning to get off somewhere along the way do not put in pack in with the luggage storage.