transportation from Bournemouth to France, and within France

You can get a ferry from Poole (close to Bournemouth) to Cherbourg with Brittany Ferries to get to Normandy. If you want to go straight from there to the Loire you'll want to hire a car as the French transport system is very centralised and its hard to get anywhere without going through Paris.

As Philip said, there is a ferry from Poole to Cherbourg, but if you want to arrive at a port with a TGV connection then you need to travel from Portsmouth and go to Le Havre (probably best as your onward journey will be via Paris) or St. Malo. Bournemouth to Portsmouth isn't hard (change at Southampton Central), but it's a fast catermaran service that leaves Portsmouth at 07.00 so you might need an overnight stay. Trying to think of alternatives, potentially skipping the Loire, on Mondays and Fridays there is a Ryanair flight from Bournemouth to Carcassonne, but that isn't even very close to the Dordogne. From Southampton there is a Flybe service to Bordeaux.

Thanks so much for your suggestions. Two more questions: 1.) Is the channel crossing very rough? I have a problem with sea sickness, so I'm wondering if this is the best choice. 2.) If you were a first time traveler in France, would you stop at the Loire Valley? I've had two friends tell me to skip it and spend more time in Dordogne. I, of course, want to see everything, but we only have 10 days. What would you do?
Thanks so much for your help! Robin

The Channel can be as flat as a millpond, so rough that the ferries stop running, or anywhere in between. I've crossed it in 30 foot yachts, fast catermerans and massive car ferries and I've always been fine, but if you suffer from seasickness then even a slight swell could be too much for you. Tips on avoiding seasickness: 1. Medication can be bought over the counter at pharmacies. The modern ones work pretty well. Stay well hydrated, don't eat too much and stay away from greasy foods or anywhere on the ship where you can smell food being cooked and served 2. Stay on deck, or at least near a window where you can watch the horizon. It helps because the nausea is caused by your inner ear balance mechanism telling your brain one thing and your eye telling it another - the horizon is a fixed point that helps the brain avoid this 3. If that doesn't work, lie down and close your eyes and if that doesn't work the only solution left is to go and sit under a tree... :-) As for the Loire, I can't say I've spent enough time there to offer much of an opinion, but I think I'd focus on the Dordogne, not least because I like the wines from down there.

Thanks, Kevin! I appreciate the advice. I think the Channel is our best best, so I will come prepared and hope for the best!

Given your short time span and deep ambitions, I should look into FLYING from Britain to Toulouse or Bordeaux, both about 2 hours form the Dordogne. Rent a car to see the area and drive north. Your route should probably be Dordogne/Loire/Normandy by car, then either drive or take the train to Paris. With only 10 days I would prioritize as follows: Dordogne, Paris, Normandy, Loire. I'd say skip the last altogether except it is dead enroute. So spend a night and see one chateau; if you really like it plan to return. The TGV does not really help you this trip.