Books on Board's UK site also has them but slightly more expensive, even with their rewards rebates. They can all be advance-purchased, but the release dates are staggered - some are on sale but won't be released until November 2010! Which seems a bit odd, to say the least.......
It's a shame the only format is Adobe Epub. I've just bought two K.J.Parker ebooks from BoB and have emailed them to complain about the formatting. The basic font size is so small I need a magnifying glass but when I increase it to a readable size I get 6 words per line, acres of white space and no justification....sigh.....