How far have you got to go, Greenockgal? If it helps, here is my 'size 14' story. A LL friend (from my group) gave me her size 14 work trousers and jeans - really good brands, and she couldn't bear just to throw them away - when she grew out of them. This was in, maybe, October and I was about a size 18. Every few weeks I tried them on, and at first I couldn't even get my legs into them, let alone my big butt. But gradually I got them further and further on, and just before Christmas there was about an inch before the zip would close. By new year I was wearing them all, but now, a month later, they are falling off and I've just bought some M&S 12s.
That's how fast this works. From hopeless to too big in about 7 weeks. So just keep trying it on and in no time it'll fit. Sounds gorgeous, by the way. I love Karen Millen stuff. Hey, that's an idea!..