I understand that Nov 1 is a national holiday in France (and Belgium). Does anyone know how that effects museums, sights, dining, shopping, entertainment, etc.?I know that the Eurostar has some reduction in service.
Several years ago, I was traveling by train from France to Italy on November 1st. It seems to me that it was quite a significant holiday - lots of families, lots of crowds. Also, if you are looking at this coming Nov 1st, it's important to note that it falls on a Tuesday. In France, there is expression "faire le pont" or making a bridge. If a holiday falls on Tuesday, Monday will also be a holiday.
Check the websites for the particular museum(s) you are interested in. Many smaller museums will close on that day. Any place that has a separate schedule for holidays (jours fériés) such as the train will be on the holiday schedule. Shopping will depend. Some businesses will stay open, others won't. Some will post a sign on their door letting you know a few days in advance, others will just assume you know what they always do for the holiday. It is a 4 day weekend for most businesses, and the end of a period of school vacation for all schoolchildren. (Other vacations such as spring break are staggered for different regions of the country) I would expect a lot of traffic that day.
We picked up a rental car in Paris a few years ago on Nov. 1 to travel to Germany. We were delighted at how light traffic was that day. It was a huge break for us as traffic we had seen in Paris was pretty frightening.