No longer! The other night I got mine out and had a think. I puzzled and puzzled, I drew up a pattern that had darts in it to get it to fit the angled sides. Nah. I puzzled some more. Then I went and googled 'mug cozy' and one of the returns had a curved template. It was for a Starbucks cup I think so not much use in practical terms but it was a "ah HA!" moment. But how to get the curve? So I thought a bit more and then realised I could roll the mug across a piece of paper and trace it and so the mug cosy pattern was born! After that it was simple as. A couple red buttons from the button box, a bit of red running stitch and I'm in looooove.
I'd like to make another one for Mat's mug - his is flat black and unglazed - well the shiny glaze anyways. I might document that one for a tutorial kind of thing in case anyone else is puzzling as well. I still find the shape of pattern to be somehow counter-intuitive although I can see the logic in it if I force my brain!