For convenience you may not want to avoid all toll. Calais Rouen Chartres, Tours, Poitiers, Bordeaux. If you look at map you can see you can avoid main toll sections between Bologne Abbeville. Then between Tours Poitiers but it's slow. Then take toll free dual N10 between Poitiers & Bordeaux. The non toll roads follow route of toll sections so you can get back onto fast rd if you get bored. After Bordeaux a bit of toll but not much.
Thank you for all of your replies we had more or less decided to have a mixture of toll roads and non toll roads but as it is our first drive abroad I just wanted reassurance from the very knowledgeable people on here and you haven't let me down. We aren't towing this time but have decided to go for a Eurocamp mobile home.
maggieabbey,
have a look at the 'about france.com' website, it gives useful info on routes and suggests tolls, non tolls and both combined. It will also recommend using tolls to save considerable time against small toll charges.
Basa