Not wanting to wait that long I managed to find an RTM copy of WIndows 8 Pro 64-bit through a certain torrent sharing website, which downloaded overnight. As the technician suggested, I was able to make an install DVD from that, which I successfully installed and activated this morning using my (legitimate) product key.
Where did you download it from?
I have read before of non genuine versions of windows (made out to be just copies) being infected with deep-rooted spyware, including keyloggers etc.. This will not be picked up by your normal ant-virus and anti-spyware programs.
Personally I would never trust a OS downloaded from a third party website. But thats just me..