Not sure exactly what you have done.
Did you delete the partitions from booting W8 Install setup (or other partition manager)?
Did you actually try to install W8 and the restart was part of that process?
Anyway, try Minitool Partition Wizard Bootable CD on a disc or USB drive and see if the Partition Recovery Wizard can get you back to normal.
I'm afraid I don't know the ins and outs of grub