Looks like I might have been the first person to spot this.
The soundtrack DS did for the 'When loud weather buffeted Naoshima' installation will be released on CD (sound cd ss0011), seemingly not (or in addition to) as a download from the Sylvian site.
So, there you go.
http://www.davidsylvian.com/other_writings/david_sylvian_biography_july_2007.html
Hurrah! Got my ticket finally for the festival hall. Thought I was going to miss out too!
Cheers all
C x