My only experience with a wool/cotton blend was a disaster. I used Noro Chirimen for a cardigan, Bettna, and it stretches out of shape when worn. Ugh. Since this is my second disaster, I've steered away from any animal fiber/cotton blends.
Maybe if the blend had been 60% wool and 16% cotton...it would've been a different story. I dunno. But I don't want to take the risk. I like blends just fine...but I leave cotton out of the mix when wool is present.
Here is another disastrous blend of cotton and wool: Debbie Bliss Cotton Angora
The cardigan, Phoebe, stretched like crazy. I use it for a bathrobe when we're camping, and no one is around but me and DH.
Debbie Bliss Cotton Angora
80% Cotton, 20% Angora