Damn, that's harder to figure out. I'll keep looking and see if I can get hold of a mac to try and work out what is growing on. Until I can, unfortunately the only way to play is with the windows version.
Thanks for the suggestion!
I have turned off the appstore validation like you suggested and also uploaded multiple versions of the Mac file (for different versions of the mac operating system) so if one doesn't work, hopefully the others will.
Let me know how it turns out.