The first mistake was misreading my sketch. I had originally wanted to put a flange border around the centre, but instead put a normal border in. I then put the flange border around the outer edge, as we wanted the darker colour to framed the blue, but I forgot, cushions aren't flat like quilts.
I was going to change it, but Tracy liked it as it is. I've used a stitch in the centre of each side to keep the flange forward facing and it does have quite a good effect, just not what I was expecting. It just goes to show, sometimes mistakes can sometimes turn out well.