Gog provide offline updates for "1.00 to 1.01" and "1.10 to 1.31", but the "1.01 to 1.31" is only available
via Gog Galaxy, which DELETE the installer just after the install is done. How the hell I can't keep this
specific update ? How is it possible to enjoy downloading 10 giga of fixes every-time I reinstall the game ?
Regards.

I don't use Galaxy but I know that you should be able to download backup files with Galaxy too (more-button).
Otherwise download and keep the files for later use with your browser from gog website or use the GOG Downloader.