There is a lot of forest in the Landes region of France, and so many houses are heated with firewood. Buying good wood is not as easy as it sounds, and trying to buy it out of season is difficult. Good wood should have been dried for at least six months, and anything up to three years.
You should order wood well in advance as it can take up to one month to deliver. Ideally order in the early spring so that it has all summer to dry out. Ask your neighbours where they get theirs, check the local newspaper small ads or look for signs by the road. The best wood to burn is oak, although it is slightly more expensive it give you more heat.

Here are the basics of buying fire wood.
Fire wood is measured by the stere. 1 stere is approximately 1 cubic metre.
Expect to pay between €45 and €55 per stere, delivered. Oak is the most expensive. Most people buy a mix.
Depending on the size of your house and the efiiciency of your fire between 5 and 10 steres should last a winter. Ask your neighbours, they probably have a similar size house and will be able to give you a good idea.
Buy your wood in the early spring and stack it neatly in a dry area, inside if possible. If outside, cover the top with a polythene sheet or "bache" weighted down with a few logs, but leave the sides open allowing plenty of air to circulate and help dry it out.

How to burn it.
Surely you just set fire to it and then walk away? NO.
Older houses will have a plain old open fireplace. While this is probably the most aesthetically pleasing option, it is not the best. An open fireplace is probably only 30% effective at capturing and distributing the heat from your burning logs. It is also highly inadvisable to leave the house with a fire burning in an open fireplace. Even well seasoned dry wood can occasionally spit large sparks or glowing coals from the fire, and this is an incredible fire risk.

A wood burner is much more effective at around 70%+ efficient. We have a glass fronted wood burning stove with a door that locks, giving us the benefits of a lovely fire burning in the room, that we can happily leave burning while we are out. This is backed up with a fan system that literally pumps hot air from the fire around the house. Our house is around 100m2, and three or four medium size logs heats the whole house in a very short time. I estimate this cost at around €2.