This is actually a write up of a fix for a rattle that I haven't seen documented elsewhere. I spent ages tracking this down and thought it might be handy if anyone else hits this in the future. Note this particular issue will only affect the 3 door.
Symptoms are an intermittent, metallic rattle/clicking from the rear quarter. Sometimes it's louder than others. It can also cause a creak over uneven surfaces at slow speeds (such as driving onto a steep driveway) or even when pulling away or under braking.
So really it's a fairly traditional rattle but combined with a creak when the car's body flexes. None of the other common things people raise (such as the boot bump stops, or the rear seat latch) work. The fix is fairly invasive with the trim you have to take off so don't do it on a whim! Ride around in the back while someone else drives and ensure it's coming from the door card/rear window area.
What this was eventually tracked down to is the sheet metal around the rear window. This is why it will only apply to the 3 door as the 5 door has... doors where the 3 door is obviously a permanent, welded structure.
Now I can't be very specific on which sheet metal it is (and I daresay it could vary per car) because while I had panels off, I worked on various. But effectively, anywhere two or more pieces of sheet metal around the window come into contact and can easily be adjusted, I put a small flat head screwdriver between them and lightly "separated" them. This sounds more severe than it is... Really it's just to try to remove any tension between them and doesn't require lots of force. Sometimes you'll almost hear a click as you do it. I also sprayed silicone lubricant anywhere I could get between the sheets to try to help reduce friction.
To do this, you'll at least have to remove the B and C pillar trim but I also removed the rear "door card". While some of the sheet metal goes under the headliner, you can just about get to it without removing the liner. With the B and C trims of you can pull the liner away enough to get access.
As I say... You'd want to make sure this is a possible issue before going to all this trouble but I wanted to get a post out there which explained this very niche problem and possibly save someone's sanity.
