Batting

It's made of polyester and you'll find it in a patchwork shop or in the haberdashery department of a department store like John Lewis. It will be called either quilt batting or quilt wadding. The one I got was "Soft and Bright". It's about 1 to 2 cm thick - if it's at the thin end of the range you might want to double it up.

There are also battings made of cotton or a cotton/polyester mix. But normally it's used to make quilts with.

It's basically a sheet of stuffing like you would use in stuffed animals, just it's in sheet form so you can cut it and use it for quilts and such.

Thanks for all the info jabber, Ly & Rach. I have ordered some cotton for the outside and the batting for inside, and have already got lots of fleece to line the inside of the cuddlecup, so will get started on my first one this week! If it works out I'll post a pic.