Le Ty Nadan is between Quimper and Lorient and is a campingcheque site in low season so if you are going low season its a good deal. It has good reviews on the campingcheque website so check it out.
bois-des-ecureuil is a great site 20k north of Lorient, Check out my review. My only complaint is that we aren't going this year! heading further south for 2012 but we have it firmly in our sights for 2013. Been a couple of tiomes and love it.