My go to standby is a maxi-dress with a shrug, and pretty ballet flats :http://www.ezibuy.com.au/brands/sara-plus-...le_s_style_maxi
I think this one is very pretty and you could wear a pink, peach or green shrug to go with it :http://www.ezibuy.com.au/womens-clothing/d...dress-88216.htm
I'd get the shrug in fine wool/cashmere from Woolovers. They're much cheaper than the equivalent Australian knits, have a wider range, and they get here in 2 weeks. The XL should fit you - it fits me and I'm a broad shouldered size 20.
This one is very pretty - it also works untied:http://www.woolovers.com.au/cashmere-merin...p-cardigan.aspx
But Ezibuy does have a good range of shrugs (73 to be precise) so check them out too
Search under "Bolero".
If its really nippy, I'd wear leggings under the maxi-dress: something you can't get away with in a shorter dress ! You can also add a Pashmina if its really cold as well... Not to mention a strappy thermal vest
I know this sounds a bit odd - wear a floaty dress and killer thermals, but it's what Europeans do - wear "normal" clothes and then thermals underneath. Much better than putting yourself into a pantsuit, or shivering in tights and a short skirt.
Oh, and if you have money to burn:http://www.igigi.com/plus-size-dresses/mariella-gown.html