Where do your purchase train tickets for a one way ticket to Paris from Bordeaux?
The French national rail site at TGV-Europe. Keep setting your country to Great Britain or Canada (so you don't get kicked over to RailEurope) and you'll be able to choose from a wide variety of schedules and fares. Some tickets you can print out at home....others you can pick up at any train station ticket office with your e-mail confirmation and the credit card you used to purchase the tickets. Some great advance deal can be found on many routes....just make sure you read the refund and exchange conditions.