So this was quite easy - but time-consuming and painful.
1) Remove bumper as per the article posted
2) Drill several large holes through both skins of the trunk so you can access the lock mechanism
3) Shape a coathanger to grab onto the pin (the wires had both fallen off)
4) Fiddle and fiddle and fiddle until you can pull the pin with the coat hanger
That's really it. Here's a picture of the ugly holes I made behind the bumper. You can't see them once it's all re-assembled.
