I have to agree with the suggestion to use flannel whole cloth as an alternative.
(in the UK, look for a superking brushed cotton flat sheet or even a brushed cotton duvet cover that you can cut apart.)
Quality Flannel/brushed cotton has become my default batting material. It’s cozy, it’s warm. It’s wonderfully cuddly. It takes a hot cotton wash without any issues. And because it is woven fabric instead of traditional batting, you don’t have the stability issues or quilting distance requirements some battings need.
It would be be helpful if we could see a picture of your quilt top, to make suggestions on the actual quilting pattern.