To remove the lock, unhook the rod and undo the two screws from inside the boot lid.
Rotate the lock and withdraw it, and unplug the multiplug.
Remove the circlip and remove the end plate. Turn the end plate upside down and the circular spring is there.
Best bet is to get a replacement from the scrapyard and swap bits over, then you get to keep your key.
It's very simple once you see it in front of you
I had mine in bits for the umpteenth time yesterday, there's a small casting inside which breaks up and causes the symptoms you describe.