For travel on the Eurostar and french TGV trains. it is essential to carry your bike in a housse a velo - a bike bag. They simply don't have the space for fully assembled bikes.
Eurostar
The Eurostar is essentially a french TGV train and therefore the same rules apply. They do however have a small storage area/guards van which you can put bike bags in. On both occasions we were refused access to this area at first and had to push hard to get the bikes in.
Paris Metro
This is hard work. The Eurostar comes into Gare dy Nord and the TGV for Bordeaux/Toulouse etc lease from Paris Montparnasse. This involves a ride across town on the No 4 line. Getting to and from the platforms is difficult with bags - you need to get the gates opened to allow bags through the turnstiles and there are many stairs and escalators to negotiate. Allow an hour at least between trains. On the metro itself, each carriage has three doors - try to get one of the end doors - if you're in the middle you will be cursed at as you push your bike around!
TGV
As mentioned, you must have your bike in a bike bag as there are no guards vans for bikes. Each carriage has a large luggage area which will just about accept a bike bag lying flat. However, try to get your gear on as early as possible - the best way to descibe the scene is a rugby scrum. If you are last on you will probably have to put your bike bag in the aisle if the train is busy increasing the chances of an argument with another passenger/SNCF official not to mention damage to your gear.
We planned to leave our bags in the train station left luggage for the 3 weeks we were touring but this proved impossible. Bordeaux station (like many others) no longer has a left luggage facility but has lockers only instead. The maximum time permitted for storage is only 3 days. We had to persuade the staff at the excellent nearby Hotel Royal St Jean to look after our bags while we were touring.
Local trains
We used the local trains (T.E.R.) to hop between towns such as Bergerac and St Emilion. Taking a bike on these couldn't provide a greater contrast with the TGV. Again however there was some confusion over the exact method. We were originally told by a cashier that all trains carried bikes. This later proved to be incorrect. To be sure, check the actual printed timetables that you can take away - those on display in the station did not have the information. Approximately 75% of the services carried bikes. It is free. Simply remove panniers and the bikes go into a special area and hang up by the front wheels. These trains were all brand new so there may be different storage areas on older trains. They don't stop for long at the smaller rural stations so you have to be ready to bail out quickly!
Overall we found the local trains excellent and the TGV/Eurostars harder but worth the effort. Crossing Paris on the Metro is daunting with such big luggage and lots of walking but can be done if you grit your teeth and just do it.
Hopefully this is of use - if you want additional info, please E-MAIL ME.
Darren Martin PS Visit my Tour Report