We toured Channel to Med this year, mainly camping. We always seemed to be out of synch with shop opening hours around lunch time (12:00 – 14:00). When we were ready the shops were shut and when we weren't, they were open.
We normally start around 08:30, stop for a snack a couple of hours later then stop for lunch a couple of hours after that – right in the middle of the lunch time shutdown. We normally don't eat cooked food for lunch, just bakery or supermarket (Boulangerie et Supermarche if you prefer..) and most of the places we stopped were quite small so not much choice/many alternatives.
Personally, I'd also avoid the F1's like the plague. Yes they are cheap and convenient but as commented above, they tend to be out of the way (i.e. usually souless retail parks on the edge of town) and just not very…French. Get into town to the local hotels etc and meet the locals 🙂