A site I came across as a spin-off from watching Sewing Bee was www.lekala.co/
They sell sewing patterns, but more important, it is possible to design your own dress and feed your own measurement in and print off the pattern onto A4 sheets that you stick together.
You go through each element, for sleeves, for example, length, arm/bodice fit, cuff finish and so on with skirt, top etc etc, feed in your measurements and abracadabra.
Obviously, if you want something really mad like Farie's single wrap round sleeve, you will have problems. But DD made me a dress using it, and I am very happy with it.