When I travel I bring plenty of EmergenC packets. They help with the jet lag, dehydration, and immune response to new alien proteins and toxins. The C will help with cigarette smoke too.
Definitely bring something that aids BMs, any break in your regular schedule can cause constipation and that's just miserable to have to deal with in a foreign country! My personal fave is Sonne's Perfect 7 Intestinal Cleanser. It's psyllium, bentonite, and cascara sagrada in capsules so they travel well. Cascara is my personal favorite laxative because it works really well without causing cramping. It actually encourages the colon to produce mucus, which for me being a total Vata is a very good thing because my tissues tend to be too dry. Just one capsule will keep me very regular.
You should be able to find excellent digesive aids in France if you need to. When I was in Germany I found that most of the digestive aids are herb based, unlike our typical Tums. Their remedies use a lot of peppermint, so they're much safer to use.
Oh and bring chamomile tea to help with the time change and insomnia. Hopefully you'll have a tea caddy in your room and can make your own tea no problem. I usually travel with a selection of teas - chamomile, peppermint, ginger.
Bon voyage! :)