My experience doing this was super easy. I called airfrance and they scheduled me on a direct Delta flight to Paris. The flight was very good and everything in the airport was really easy. My dog was exactly 18 lbs with the carrier. There was no further customs in Paris.
Folkestone pet taxi (
http://www.folkestonetaxi.com/Pet+travel+abroad.html) was AMAZING. They picked me up in Paris and drove us to the pet reception at Calais. I was super worried about our paperwork since my dog had a 9 day lapse between his most recent rabies vaccine (given more than 1 year ago) and his previous rabies vaccine. I did not have any problems at the pet reception though. We rode with folkestone taxi on the train and they dropped us off at a car rental place in Dover. We drove the rest of the way.
I totally recommend this. I shipped my pets via Heathrow in 2012 before and having my dog with me also saved a lot of time. I didn't have to drop my dog off 4 hours in advance and I didn't have to wait around for a couple of hours (I swear we waited 3 hours after our flight landed, granted we had 3 pets) at the pet reception in Heathrow. This meant my dog was in the crate, albeit a much smaller crate, for a shorter period of time.
