I had this problem just the other day. I went to the green box embedded in the ground and removed the lid. Along with the handle that turns the water on and off there was a silver valve which had a hole in it but there didn't seem any way of adjusting it. I called the guy who installed it and he came and simply unscrewed the top of the valve so that it came off like a ten pence piece. He then put a screw driver into the opening below and turned it. I had the tape on so that we could see the change in pressure. Hope this is of some help.
Although I normally fly into Bordeaux airport, now that I'm thinking of getting a car, Bordeaux doesn't do three month parking passes. Someone told me that Toulouse does, is this still the case?