I expect you've left already, I hope you found a good route.
We go this way:
Calais/ boulogne down to Abbeville.
Rouen.
(Now pay attention, this misses Paris and is stress free)
Everux.
Nonancourt.
Dreux.
Chartres.
Orleans.
(Back on ''normal route'')
Verzon.
Chateauroux.
Limoges.
Brive.
Toulouse.
St Gaudens.
Vielha.
After Vielha is the tricky bit for you. You have to get over the Pyrenees some how!
The views are lovely. The road does twist some what, but most of the way there are lakes not very far below you. It's not very long (maybe an hour) untill you're on level ground again.
After that it's down to you. We live 4 hours from Vielha and don't go any further down!
Tolls are around 40 euros.
We do this in an easy one night stop, mind you, we are in a subaru WRX STi! No even in the landrover it's a one night stop. Two if we want to take it easy.
Hope you have/had a good trip.
Take care,
Febe