I've just been looking on the DIsney web site and it definitely says that Fantillusion starts from 5.11.05 - surely we can rely on their own website???
Yes, it starts november. I've checked with friends at the entertainment department. They confirmed november too. It's probably a typo in the Benelux catalogue.
I reckon that Tour Operators were told that Fantillusion may start in November, but would definitely be on from the beginning of December - so they print the later date, as they don't want to run the risk of having upset clients.