Paris and the Heart of a France tour ?

I've been to France several times in May/early June and it is beautiful!

I've been to France in October and can tell you that it gets dark pretty early. Also we had some rain and it was cold. In May, the days will be getting longer and warmer, though you could still have rain. My vote is for May.

We did the RS Heart of France tour last May 2014. The weather was fairly nice. It really rained only one day, but we were probably lucky. I think that you can get heavy rain either month. The main advantage with May is that the days were longer, the sun not setting till after 9 pm. Just bring appropriate outer clothing.
The only place specifically on the tour that I recall where photography of any sort was banned was when we saw the Bayeux tapestry in Bayeux.
Finally, I don't recall any stops which were not listed on the schedule. However, the towns listed are all very charming and small, which is a sharp contrast to Paris (charming but big). I would definitely consider the tour as an option. We particularly like Bourges. There was a fantastic 1 star Michelin restaurant in town where we had dinner for our anniversary, made it really memorable. It was Restaurant d'Antan Sancerrois. Reasonably priced considering the quality of the food.

I was on this tour last October. We mostly had comfortable shirtsleeves-weather, with just a threat of rain. There was significant wind and some periods of rain at Mont St. Michel and on the Normandy beaches.

A couple of years ago, our marketing department made a move toward fuller itinerary listings online (and fewer surprises). Your town for a Brittany lunch stop is guide's choice and our stop was equally as charming as other towns of the tour. I can't recall any sites that did disallowed all photography, but most do disallow flash.