My XJR seems to have gotten an interior swap at some point, and, forgetting that this has happened, I managed to luck the glovebox with my black key and now it won't unlock. Dealer can't help, and I have no idea where the donor car is to get its key. Do I have any options short of drilling out the lock or otherwise destroying the glovebox? I tried unbolting it from below, but the latch is separate, so that didn't help.

EDIT: Managed to manhandle it open, breaking off one of the mounting tabs for the glovebox handle, and removed the locking mechanism so it won't happen again. Now to see if I can epoxy the handle back together.

Just a note to whoever comes across this in the future, it is possible to remove the entire glovebox from the car and then disassemble it without breaking it into pieces
Bit of a pain but there you go.

The Tibbe locks on these cars are an easy pick open. Any competent auto locksmith will be able to open and decode the lock and cut a new key.