Is City Wonders a reputable firm to do the 1/2 half day Giverny Monet's house and gardens tour?
This is one that makes no sense to pay extra for a tour; just get tickets from St. Lazare to Vernon and for the bus that goes from the train station to the gardens. You can stroll at your leisure and the buses and mini trains are timed to the return trains. (if you use the mini train be sure to step lively on both ends because when it is full, it is full. On the bus you have people standing in the aisles, but on the train, if the seats are full you don't ride.
We have done it twice on our own; it is very easy to do.
I echo Janet's sentiment. The problem with these tour companies is that you take a bus through miserable Paris traffic and by the time you get there there's little time to see the places. I did this on a trip to Vaux-le-Vicomte at Christmastime once and really regretted it.
I'm a solo traveler and managed the transpo to Monet's house and gardens a few hrs ago. It was a good experience. The gardens are lovely. I suggest arriving early as it gets crowded and the views are lost. When I visited, I noticed his photo on the wall in the kitchen. He appeared to be a larger man than I expected. I bought a "Monet" design t shirt in the gift shop and still continue to enjoy it.