Hello Dotty,
Just over a year ago I made a load of tea cosies using thermal curtain lining for the inner layer. It's cheap as chips, there's no need to quilt it, and it's stiff enough to make the tea cosy stand up (more or less) on its own.
Lots of experience with tea here! Drink it by the gallon. I was knitting tea cosies by the time I was eight. Great way to get experience knitting with two colours.