Warm & Natural Batting
I don't know why I didn't think of this before, however after I got frustrated with every website and book telling me different standard sizes I kind of gave up. Today while in Spotlight looking at batting I noticed some pre-cut packs of the Warm & Natural which had the sizes marked, which is a brand or type I had been recommended on a quilting forum.
Craft - 34" x 45"
Cot - 45" x 60"
Twin (Single) - 72" x 90" or 180 cm x 220 cm
Double - 84" x 96"
Queen - 90" x 108"
King - 120" x 124"
The price for a twin size is just over $50 for the Warm & Natural (a cream colour) or just over $65 for a Warm & White which is apparently designed so that the batting doesn't show through lighter colours (whites and pastels) and alter or darken their appearance.