Thanks Filipe.
If the view from the N108 is as good as the minor lanes to the south of the River then I will switch that to plan A. N108 seems to have no less bends however.....how busy does it get on a Saturday in September?
If you have never done the N240/N260 Pamplona to Andorra then do it this year... its 428 Km so spend the previos night in Pamplona and plan to spend the next night in Adorra la vella.
http://tinyurl.com/Pamplona-Andorra-N240-N260