Flannelette is the same thing as flannel. In Canada the two terms are almost interchangeable. Flannelette tends to be sold as yardage which is fine for quilt backings but would have to be seamed. I haven't had a huge problem with flannel sheets pilling or shrinking. The heavier Ibex ones (they have coloured stripes on both ends and are a creamy colour) are especially thick and long wearing. Just be sure to check the weave (loose, light or sleezy is not good)and prewash if you don't like the crinkled look in your top. I've had quilts with flannel backings stand up really well to repeated washings. They also tend to not slide off your bed as easily. Flannel sheets are also fine for quilt battings but make a much flatter quilt.