Brittany is pretty much the same as Cornwall weather wise, the Loire a little warmer and settled.
The 10 day forecast here isn't too bad after the 9th
http://www.weather.com/outlook/travel/businesstraveler/tenday/LYS:9
The 10 day forecast here isn't too bad after the 9th
http://www.weather.com/outlook/travel/businesstraveler/tenday/LYS:9