Hi Esandar.
Sounds like a nice trip. Bordeaux is a very nice stop for a day before Biarritz.
Bielsa tunnel entrance, French side. We are the dark Blue Cali. Could overnight here if you wished.
View attachment 110622If you want to cross via the high mountains then I would suggest you take the A64 towards Toulouse and turn off south at Sortie16 towards Saint Lary (there is an Aire here in the town centre which might be handy for an overnight, or you could drive up to the ski area here and stay in the car park) and on up into the mountains. This will lead to the Bielsa tunnel and then on down through some lovely scenery to join the A22 motorway west of Lleida and then the motorway to Barcelona.
I can't help with campsites around Barcelona as we always stay with my daughter but there are plenty to choose from. Roses is a way up the coast and woud add quite a bit of mileage. Sitges is a very nice seaside place west of Barcelona and is on the railway line to Barcelona.
I asked my daughter about the LEZ and she said no one seems to bother with it. She has lived there for about five years and never registered without any problems.
Hope you have a good time.