Thanks, Lee, I'd already stumbled across that one but it's still giving me issues: I got stuck at the clip that connects the lock to the outer door pull.
It is the one right in the middle in the picture, isn't it?
How exactly do I disconnect this clip? I can't seem to figure out how to knock it back, as the link you posted says.
I don't want to put too much force on it as I don't want to break it, since that would render my door entirely inoperable.