If you are driving, it takes 9.5 hours from Calais, which can be done in a day, and the autoroutes are excellent. However, it is well worth a stopover to see a little more of France. Ferries leave from Dover, Newhaven and Portsmouth. The Portsmouth route cuts a couple of hours off the journey, but the ferry journey is longer. The shuttle leaves from Ashford and takes you to Calais. It is quick, and recently the price has been almost on a par with the ferry.
I use chain hotels when stopping over, in Orleans on the way down, and around Chartres on the journey back. They are good value and I am happy to give recommendations. The TGV train stops at Agen on the way from Paris to the South, and it is possible to hire a car there. The airports locally are Bergerac, which is an hour and a quarter's drive, or Toulouse, which is an hour and a half. Car hire is available from both. I also have contacts in Montaigu who will collect you from the airport or station if you don't wish to use a car, or possibly if you wish to hire a car or bike locally. I can help with these arrangements.