We had a fantastic time staying in Saint-Mar-de-Coutais. Everything was very straightforward and as described - Ludovic's communication was excellent.
There's a great boulangerie in the village (5 mins walk), along with a little supermarket (this was more expensive though than the bigger Super-U in Bouaye a few miles away, also the diesel was pretty cheap in Bouaye).
We ate at some fantastic places, including a creperie (Le St Georges, Port-Saint-Pere - moules mariniere & profiteroles were standouts for me - thank you Martine) and a really nice restaurant on the edge of Port-Saint-Pere (Auberge du Pays de Retz, grenouilles, duck, beef and the terrine also great - be careful though the baked alaska came with enough rum to push you over the limit though).
Pornic was a delight (we drove, but there is a train there also) and my wife and daughters loved shopping in Nantes (35 mins on the train) - the station is perhaps no more than 10 minutes walk away, although the superb SNCF trains are bang on time, they don't run that often (perhaps 90 minutes).
If you goto Pornic, time your trip with the tides, you probably want to arrive 2-3 hours before high tide - and there is a lovely set of sandy coves on "Boulevard de l'Océan Sainte-Marie", no problem parking on the left hand side (we parked outside #25) of the one-way road and walking down a set of stairs to a sandy cove.
We didn't use the gas BBQ at the house, although we did have breakfast (more brunch by the time we got up) and supper on the large table outside. The house is great, clean and had all the required conveniences (dishwasher, washing machine, Wifi etc..). Largely electric security shutters and the really nice nature of the area made us feel very secure.
We didn't see any other foreign tourists and very few people spoke good English - which was great - it's surprising just how much school boy French I remembered, and as the people were so lovely no-one minded our efforts!
The roads, wine, cheese, pain, people, house and the weather were all amazing, I look forward to returning to the area as soon as possible - merci beaucoup Ludovic.
Ben, Viv and the girls.