Hi Keith-
Thanks for reaching out, I am sorry about the frustration using your UK address to make a purchase. I tried to enter a UK address in Kent, and I see what you mean.
You’re right that the drop-down list is still full of US States, even when United Kingdom is selected as the Country. However, you’re still able to type in “Kent” rather than choosing from the list. You should be able to enter in your full address in Kent manually.
I agree that this is a big user-experience issue, and I’ve filed a ticket to the developers of our payment processing system to get it fixed in the future.