The UK edition of Columbine is out of print (and lacks the 50 pages of new material), but most of Amazon's non-US country sites offer the U.S. edition, with reasonable shipping options.
I created a new Buy Columbine page, with direct links to the expanded Columbine edition on several country sites, and more info on how to make sure you're getting that edition. (I keep adding country sites as I find them: Italy, Brazil, Mexico most recently.)
There is also info there on getting an autographed copy of Columbine.
Update: And now I've added information on translations, including the new Korean translation.