Ok, Cats...I have looked at the website and I can tell you that this shop is located in a very well-to-do section of Portland and it does look like quality merchandise. I also noticed that they give a flat rate for international shipping of $40, which, considering most of the capes are $300+ really isn't that bad...but has been mentioned, Jacqui travels from Maine to the UK twice a year...
I would say the size really depends on how long you want this cape to be on you. If it's just a straight cape I would say judging from your height that you should be OK with a "long" as the extra length will be taken up by the 2x requirements...but it may be worth going someplace over there and trying one or two on before ordering...