Elizabeth
We've taken our two labs in the van to france and spain several times and it's genuinely no probs at all.
Just make sure their pet passport is in apple pie order and any other paperwork - and altho' you shouldn't need anything else these days it might help in resolving unforeseen issues if you have insurance certs, proof of ownership or whatever, altho these have NEVER been asked for in our travels to date.
Obviously the dog must have a documented (and working!) microchip, plus a valid rabies test which takes 6 months to become valid from initial date of vaccination verification before you can travel. Take care to get the booster administered within the prescribed date 'cos they are really pernickety about validity - if you don't keep it up, you will have to start the process all over again and not be able to travel with your pet (or at least not bring it back to the UK) for the full 6 months.
The main thing on returning is to ensure that you go to an approved french vet more than 24hrs from French departure time back to the UK, and less than 48hrs, but this is easy.
If you log in to the DEFRA site it has a link to the french equivalent of yellow pages - just type in the nearest town you expect to be at within the above times and up comes a list of suitably qualified vets with addresses and a downloadable location map. Site owners we have been at from the Loire northwards have always been helpful in assisting making appointments if you have any difficulty with the lingo, and we've always been seen by the vet at short notice OK.
In theory you can buy the tick and tapeworm drugs yourself more cheaply over there, for the vet to administer, but it isn't really worth the hassle. French vet fees are anyway generally a good deal less than here, particularly in rural areas.
Immediately prior to initial return check in gates for Chunnel or ferry you will see signs to the pet control facility. Plenty of room to drive and park up your van, and normally only 5mins or so to check out the animal and that's it!
Small effort for max pleasure sharing your continental hols with canine family members! The French are dog crazy and you will find they are accepted in many places you can't take 'em in the UK, reataurants included. Have a good one and bon voyage!!!!!!!!!!!!.