I have a Macbook Pro Retina Mid-2012 edition running OS X Lion 10.8.5

I recently tried to upgrate to Mavericks OSX, howeve this resulted the installation not accepting the Mac Hard drive as a viable place to install the upgrade.

I subsequently used an external drive (formatted and set with a GUID Partition table) to accept the Mavericks installation - it did, and did install in a breeze (in a partition which we shall call Mac Boot.

Furthermore, I directed the startup disk utility to boot from Mac Boot instead of the Mac Hard drive.

On bootup it installed nicely, however I was prevented from installing Mavericks on the Mac Hard drive from this Mavericks OSX build (on the external drive).

On rebooting, I realised that I could not get back into my Lion installation on my Mac hard drive - I had to go to Startup Manager every time to choose 'EFI Boot' - this would boot up Lion correctly with no issues.

On trying to run Repair and Verify operations on the Disk Utility, I could not identify any issues.

I tried to choose the Mac Hard Drive from the Startup Disk in both 1) normal Lion OSX operation 2) within the OSX Recovery service (from Startup Manager).

The results:

1) 'You can't change the startup disk to the selected disk. The bless tool was unable to set the current boot partition'.

2) The Mac Hard drive wasn't visible!

On trying to re-install OSX from the recovery service, the error ' Could not find installation information for this machine. Contact AppleCare' came up.

Any idea what the problem may be? At this stage, I just want to get back to working with Lion OSX and booting automatically without the need of the Startup Manager.