windows 8.1 media driver is missing

Ok guys so I'm trying to help my friend set up boot camp with windows 8.1 on his Macbook Air (latest version)

He has the latest version of OSX installed, all firmware and software is up to date.

We're trying to install Windows 8.1 Pro 64bit from an ISO (genuine with key, provided by Dreamspark), but running into errors:

For the first 2 days Bootcamp refused to recognize that it was a 64bit version of the ISO, this miraculously resolved itself yesterday afternoon.

Then Bootcamp failed to complete the partitioning phase, forcing us to quit and have to repair the system partition with disk utility.

Now, boot camp will accept the ISO, complete the partitioning, and reboot to start the windows installer which fails before the "select where to install to" part, with an error stating that a required media driver is missing.

We have tried redownloading the iso to rule out corruption (it works fine in Virtual Box), manually downloading the apple support drivers onto a usb thumb drive (windows cannot find the driver it needs from this, presumably because they're packed as installer files).

The next logical step I can see is to create a bootable usb installation media from the ISO and install manually without boot camp, but boot camp doesn't give us an option to create the media and I'm unaware of a 3rd party option available on mac.

Please help us, this is getting very frustrating!