If you take the ferry to St Malo [if you spell it that way it's easier to find on the map] given that you only have 12 days There is only one time saving sensible route to take down to the Spanish border and the Pyreness.
St Malo N137
Rennes N137
Nantes A 83
Niort N10
Bordeaux A63/N10
Biarritz N10/A63
Spanish Border
Spain
It really very simple from follow your noise out of the port area up the hill out of St Malo you will pick up the signs for Rennes and the dual carriageway on the outskirts of Rennes turn right or east onto the Peripherique (ring road) whatch for the sign Nantes
as you near Nantes again turn right on the Peri' your virtually going north to south of the city just keep going you go over the big bridge with the Loire below within a couple of miles you'll see the first sign for bordeux now you've got a good few miles in front of you. The motorway skirts around Niort and you join the N10 That comes down from Paris as long as your nose is pointed in the general direction of south keep going as you get near to Bordeux and see the Peri' this time your going left-clockwise if you picture yourself at 6 o clock. The road takes you up and over the road you have just left. This road is allways very busy regardless of what hour you get there. Do not let it phase you its a big city you cannot feasable by-pass it just pick you lane(not the nearside one if you do you will spend the next 20mls sh..ing youself what with drivers leaving it while the last minute and swerving of straight in front of you and other silly ba..ards joining that either do not use mirrors or are driving as if they were wearing blinkers) you are going to come of at junction 10 and go down the N10 however fear not if you miss that a few miles further on you can join the A63 motorway it will take you down to the N10 it's 6 of half a dozen of the other which route you use they both end up going to the border.
Once you get to Biaritz and the Border it will be time to play take your pick.
You can go through the border heading towards Santander and beyond that in to the area known as the "parc de europa" there are some amazing rides and beutifull scenery.
You can stay on the French side and work your way along the Pyreness heading in the general direction of Lord's and Toulouse
Or you can go into Spain following the Pyreness in the general direction of Pampalone.
If it was me I would pick either the first or second choice.
Of course you and the lady could could say stuff the morgage, kids, and lousy weather and just keep going in the general direction of Sydney.
With regard to the time it will take you to get there. That of-course depends totally on you. But if you want a rough yard stick to work of. At one time in my somewhat dubious past I was a truck driver I used to occasionally run out to North Africa when I did this run I used to use the St Malo ferry driving at 55mph in a 10 hour shift I would allways expect to get from the port to just through the border, on a good day I would manage about another 30mls. If I can do that with 44ton you should find it easy on the GS. The drive down is not what anybody would call scenic, so you may aswell work at it the first day that will allow you more time to enjoy scenery that is well worth seeing.
I hope you find this usefull if you should wish to pick my brains or I have left out something you are welcome to PM me, but I am going of to the south of France myself on the 28 th of May for 3 weeks. If the spelling and punctuation is crap you can blame the state education system, I allways do.
Yan you.
