There are many differences! e.g. plain flour = all purpose. I've recently moved to London and have had a hard time finding regular semi-sweet chocolate chips in the supermarkets (Waitrose does have chocolate "chunks" but doesn't work as well. (Also, unsweetened baker's chocolate is hard to find..)
Happy baking!

The always informative David Lebovitz has done several blogs comparing American and French baking ingredients, suggesting substitutions or how they differ. Two entries in particular come to mind: 'Ingredients for American Baking in Paris' compares French/American flours, dairy products, etc. (http://www.davidlebovitz.com/2006/02/american-baking/) and 'French Sugars' is especially helpful, I found. (http://www.davidlebovitz.com/2009/11/french-sugars/). He no doubt has other entries about this subject, so I'd scan his website - it's a really terrific one in any case.