The Download Instructions are a little vague to me.
GOG Site provides
Xenonauts v1.05
and only
Xenonauts v1.09 Patch
A problem if v1.08 is required.
Getting a valid X:CE v0.27 would help though I think
X:CE 0.26HF: Attachment 5098
is meant to be X:CE v0.27 making it clear would help and if it isn't X:CE v0.27 where is it
Totally Confusing me this one, it may be obvious, but naming X:CE v0.27 download link as X:CE v0.27 would be so much easier to understand.
I never expect Modding to be simple but I don't recall finding the mods download being so hard, even if the broken link worked, unless it's file name is XCE v0.27 I would be still unsure I had the right files.