Hi mate, are you sure it's the parcel shelf that's making the noise? I had some repair work done last February by my local Ford dealer, and ever since I've had a rattling sound from the rear end. Could have sworn it was the parcel shelf, but it turned out to be the boot latch. I only found out about two weeks ago after applying a little grease to the boot latch mechanism. Actually it turned out to be the rubber pieces on the bottom of the latch mechanism that was making the noise. After applying some grease to the rubber pieces, the sound has completely gone.
You may want to try that first.
I'll try to take a picture tomorrow of where I applied the grease.
Ian.