Update 2: And now it's showing up for purchase on the UK Play Store - 1000 of your pounds will buy an Explorer Edition Glass in one of five colors. The same free frame / shade deal going on in the US is also available for the UK version. (Thanks, Ben!) Here's the official UK landing page for Glass, too.
Accessories seem to line up, as well - all the shades, frames, the stereo and mono earbuds, carrying case, pouch, and spare charger are all available for purchase.