Transport from Roncesvalles to Pamplona on a Sunday

Hi All, As part of our Camino this April we are walking from SJPDP to Roncesvalles because we want to then we are starting the Norte Camino from Irun. We were going to get the bus from Roncesvalles to Pamplona and then bus or train to Irun. Which leads me to this question: currently we will be getting into Roncesvalles late on a Saturday which means we need to get to Irun on a Sunday. Looking at the Artieda bus timetable it appears that they don't run on a Sunday. A taxi looks like it will cost around 50 Euro. Can anyone think of any other alternatives? Is there something that I'm missing or will we need to change our dates . Thanks