PompeyPaul,
Try heading (South/West) towards Nantes - as long as you plan carefully the airspace is not too bad. Enroute there are a few places you could stop if you don't fancy all the way to Nantes. The Nantes area has a number of nice airfields and places to visit (in the office so I don't have any details with me).
After Nantes, if you are feeling really adventurous how about following the Atlantic coast down to Biarritz? Should impress the missus!
Navigation should not be too much of a problems as you follow the coast, there is some restricted airspace but if you go at the weekend it's mostly open to you. Just plan so you know who to talk to when. La Rochelle is on the way down. I have only stopped for fuel but hear it's nice.
Just plan carefully. In France some airfields are not fully open on Sundays (French on the radio rather than English) or lunchtimes. You also need to check customs, and some you need a transponder. All airfield details are on line (don't have link with me somebody will post if you want it), and large airfield will let GA in along with Ryanair!
Have fun and GO FOR IT!
Tim