I am very glad we rang the day before to confirm, and more importantly got our hotel to do it for us. Turns out there was a strike in Versailles and there would have been a chance the tour wouldn't have happened. I don't believe there was any attempt to contact us prior to our tour to let us know, nor did they offer a refund. They happily moved us to another day, which was great, and it went without a hitch, thoroughly enjoyed it! But, I think perhaps there should have been some attempt to let us know regarding the possibility of not being able to go.
The tour as a whole was great, our guides were lovely, very helpful and friendly. The group was big, but they managed well. I would say it felt a little rushed at times but I imagine that happens given the locations. I do recommend this tour to anyone who is a little unsure initially how to get around and see some of the bigger sites. Was a lovely night, and it ensured we booked to go right to the top of the Tower another night!