If you want to make a real holiday of it and add an extra day to your journey. then do go through Foix -- you can spend the night in Andorra. Well worth it for the scenery alone.also..
I tend to drive a lot faster on french autoroutes - far fewer cameras and the further south you go the faster the general traffic gets. you can easily get sucked into 90-100mph without realising it. when you get to the pyrenees, stick to motorway. follow the toulouse to carcassonne route - avoid the mountain road through Foix. looks like a shortcut on the map - it really isn't! the ibz ferry from barcelona is pretty easy - virtually no facilities at the carport though. take your own supplies. it can get very hot there whilst you're waiting.
I have a story about Rouen. One of my first "clubbing" stories, not that it was really clubbing of any description, but the absurd nature of it fits the same kind of bracket.In my experience, the fastest (if not quaintest) route avoiding Paris heading north is bcn - la jonquera - carc - toulouse - limoges (sleep) - orleans - chartres - rouen - dieppe (very nice crossing approx 4 hrs) - newhaven. Total journey 17-20 hrs