I’m adding more info to Didier’s input regarding printing service from Bordeaux University.
Here’s their advertisement attached (on the map the relevant location for us is Site Talence, it’s a small door under stairs).
You can send your requests and needs at the following e-mail.
Indeed you should send your request asap and maybe rely on another printing service as sent by Didier if they don’t reply or can’t do it fast.
Just to give you an idea I paid 36€ for a color poster A0 235 gr, but it’s an old estimate, they might have changed their price.
Don’t forget to request how you can pay (cash?), because they might be used to charge internal departments of the uni or use French checks, but less used to other payment methods.
Usually, I have posters printed by Bordeaux University Office but it needs enough time to do it.
For others in Bordeaux, for example, take a look at: