Hi
We've been taking our 2 dogs to France for 3 years now and haven't had any problems.
As JJJ says you need to PETS passport. The dog must be 6 months old before the vet will give them the vaccination.
You must take the dog to the vet in France between 24 and 48 hours prior to your return trip. They are VERY strict on this. I've had the impression that if you're 30 minutes outside this you won't be able to travel. Also, you must ensure that the vet has both signed and stamped the passport in both places. We had an occasion when a signature was missing. Fortunately, the other passport was complete and Eurotunnel gave us the benefit of the doubt.
It costs an extra £30 to bring the dog back into the country on Eurotunnel (think it's about the same on the ferries). We pay approx. €30 at the vet for the worming, tick treatment and health check. I've got no idea if this is expensive or cheap though.
France is exceptionally dog friendly. We've taken ours into motorway service stations and normal restaurants without any problem.
One point is to check local issues of where you're going. We take ours to the Languedoc region and have been told by the local vets to avoid certain areas due to the ticks.
If you have any other questions please ask.