Fantastic guide - many thanks!
And +1 kudos to yannick NR - 10/21/2014 for his second comment from the top: after struggling and failing to extract the battery by pushing up from the bottom of the keyboard, his tip of sliding the butter knife into the battery compartment on the *keys* side of the battery compartment makes the whole operation really easy. Just slide your blunt, rounded butter knife in between the battery and the black keyboard side and then push up on the compartment lip with your thumbnail to start it moving. After only a few millimeters (when you see the top edges of the ears), you'll find that there is a lip on the keyboard-side top edge of the battery holder which you can use with your butter knife to lever out the battery holder. I used a small screwdriver just to release the ears and the battery holder popped out in less time than it took you to read this comment. Better still, no force was required and the keyboard was left completely unscratched. Very happy to get my K750 back... :)