Update:
I emailed the magazine editor, Nicholas Boerma, regarding this. He just called me now to apologise. He explained that the competition prizes are not handled by PC Format directly, but the people who are holding the competition. He didn't go into too much detail, but according to the competition page, I assume it's United International Pictures, as the competition is a promotion for the GI Joe movie.
So, my anger was incorrectly aimed at PC Format. Obviously, this competition prize balls up reflects badly on PC Format and Nicholas will ensure that U.I.P resolve this issue. I update the original post with this info.
Who knows, I might get an apology printed in the next issue or even a cameo in a GI Joe sequel. Maybe have a new Joe created in my image called "HANDsolo", because he can only use pistols and camps a lot.