There is Atelier Publimod in the Marais, 26 rue de Sévigné. It's my favourite lab before starting doing my own developments. For B&W, they used to have three B&W developers, Xtol, Microdol-X (no more, I think), and a third one I forgot. The technician does automatically inspection on every roll so it's totally fine if you forget the speed at which you expose your film (which used to happen to me a lot). They are not cheap, the development of a single roll of 135mm B&W film costs about 15€.
http://www.atelierpublimod.fr/
Another excellent lab is called Processus, near the cemetery Père Lachaise. They use TMAX developer. Manual inspection can be required at no extra cost. Around 10€ for the same roll. I believe they used to print for Ellen von Unwerth.
http://www.processusphoto.com/
Then there is Atelier Demi Teinte in the 10ème (Métro Cadet). They have as developers HC110, D76, Rodinal, TMAX. Good reputation, although I haven't used them.
http://www.demi-teinte.fr/
There is Central Dupon Images near Montmartre, supposed to be very professional and very expansive. But the first time I gave them a roll of 135mm film, they scratched it and charged me 20€ nevertheless. So I went away. But your experience might vary. The girl who works there used to work for Publimod, but she got fired at some point.
http://www.centraldupon.com/
Picto is famous, but mostly for prints, I think ; I don't know if they do developments. I have never used them.
The cheapest one is called Negatif Plus, near Gare du Nord. About 5€ a roll. It's like a supermarket. You mustn't lose your receipt, for or else they would refuse to give you back the negatives.
http://negatifplus.com/
If you want something really special for your trip, you can pay a visit to the lab of Roland Dufau near Saint-Michel, one person on earth who still does Cibachrome prints. The lab will be closed in September according to him, due to lack of chemicals. Prints are not cheap, naturally.
http://www.rolanddufau.com/
I think they are easily more than ten other labs in Paris that will do E6, C41, and B&W. Perhaps by walking around you will discover a lab that I don't know.
Pay attention to the final prices (TTC = Toute Taxe Comprise), because professional labs only display prices without tax (HT = Hors Taxe). The VAT is 20% this year.