Latest progress:
1. Went to local town, but no locksmith (3 of them) could cut keys. You need a laser cutter, sir. There's no call for those round 'ere.
2. Came back, resolved to take up Brian's challenge instead.
Here's my trusty helper, trying to get into the pannier:
Screws to remove the lock+lever sub-unit:
Got the lock+lever sub-unit off the pannier:
And what the bits are:
Then looked for how to get the barrel out. No sign of any screws, etc.
Only thing I could see was what turned out to be a hinge/rod running from one side of the complete mechanism to the other, for all the levers/handles to pivot on:
Knocked the hinge/rod out with a thin screwdriver, and then stuff started moving. Hmm, there's stuff going on in there that I can't see, so how on earth am I going to be able to put it back together if I go any further. Time to chicken out. So I put the hinge/rod back in:
and
Not so easy, the handles no longer lined up, but eventually after fiddling, I managed to slide the hingle/rod back in.
And that's how it's staying for the time-being.