The dress is cut out and I've constructed the back, front twist and lower bodice at this point, so only sleeves and hemming to go, hopefully tomorrow.
I'm liking the fabric. The gold sparkles are somehow woven into the fabric, not printed on, but are very subtle, and only on one side. I have no idea how it is done but for a poly it has great hand, not plasticky at all. I think it'll make a nice little black dress with a twist (literally). Though the gold sparkles will probably make it too much for work. It should however be very flexible for events. I can see the centre of the twist being a great place to pin an accent brooch, or sew a faux jewel, and since it'll have sleeves I shall be warm enough and not be exposing my upper arms to the world.
The length does appear to be just about knee length with the additional 2.5" so I shall do a scant 1/2" hem on the coverstitch machine and hope that's OK.
So it will need black hosiery to slim my calves, but I think will be very wearable.
edited to add for some strange reason some of the colour came off onto my fingers whilst I was sewing. Not what I would expect from a polyester knit. I'll need to wash it before the first wear to avoid getting a tide mark at the neck from the dress. Very odd and slightly disconcerting.