OS X could not be installed on your computer

'An error occurred while extracting files from the package 'Essentials.pkg'.

Quit the Installer to restart your computer and try again.

... well that's what I've been doing now for at least the last 6 hours without success.

I've even created a bootable USB stick to load Yosemite (with a new installer stub), but still get the same error.

The installer log throws back quite a few errors during the install process, I have no idea why. My MBP is a Retina 2012 model

so hardware should all be up to scratch.

I can't even restart the machine (revert) as the computer now goes into a loop and will no longer start into Mavericks.

The long and short of it is, I can no longer get into my MBP. My personal HD files are all still there, but I can't get Yosemite installed for

some reason. Help please somebody!