Don't pin too much hope on the rivers. They are very clear, low and hard going especially in daytime, and of course, you have to pack up an hour after sunset when fishing rivers in France except for a few designated places. If you only have rivers to fish I'd pack a few small Ondex spoons and a short spinning rod. Chuck the spinner under trees for chub and maybe a bonus catfish.
Have a scan of Google Earth and try and find some communal lakes near to where you are staying. You'll need a Carte de Peche, but otherwise they are free fishing. Check the Plan d'Eau at each lake. They are usually near to the car parks and show the areas where fishing is allowed. Most of them have Carpe de Nuit places, i.e. you can fish at night as long as you follow the rules.
At the moment, the big fish are still in the shallow end of the lakes. If you can find a spot where the river runs in all the better. If it is more than fifty metres from where they can get their Pierremobiles (little white vans
) you'll not see another angler. Sweetcorn is probably your best bet.
Top tip number 1.
When shopping in the supermarket have a look in the pet food section for Basse Cour chicken pellets. They are in a yellow bag and you need the Poules version, not the Poulettes. At just over six Euro for ten kilo you won't find better groundbait anywhere. Catapult it, method mix it or soak it for a few hours and hand ball it in.
Top tip number 2.
Take some small hooks and tiny bait bands for the pellets. A five metre whip will also come in handy. Then save the small roach for a bit of evening zandering.
A week's Carte de Peche is around 30 to 40 euros and available at large supermarkets and most Tabacs.