I don't know why I've not got on with it, as the pieced centre is all joined together, backed and quilted, and all I have to do is add the borders. But there's the snag. I'm not really sure how to do it. So, after a lot of thinking, I've taken the plunge. I joined a narrow purple border and a wider turquoise one together and added it to one edge of the quilt, sewing through all the layers.
Then I cut a border from the backing, and sewed it onto the back, again through all the layers.
So from the front, you can just see the two layers of fabric.
Next I carefully laid a piece of wadding (Hobbs 80/20) between the two pieces of border fabric and pinned them carefully together. So far so good. Will it work? I'll let you know!