I followed these instructions from Matt Harwood and had no problems;) .......
You'll need a phillips screwdriver and a 10mm socket, ratchet and short extension bar.
Remove the taillights (2 screws on each) and CAREFULLY withdraw them, (They're on round locators that pop off and if you're not careful, pop off and chip the paint on the rear quarter... As I did )
Remove the numberplate and the 3 screws holding the numberplate lights
Remove all the screw/expansion clips, (rawl plug type things), on the top. (3 under each taillight and 3 at the top between the lights.
Remove the 10mm bolts, (1 each side), in the top corners on the inside edge of the rear quarter and the same at the lower edge of the bumper.
Remove all 4 expansion screws from the retaining strip at the bottom underside and remove the bar with poppers attached.
Remove the expansion clip just above the exhaust pipe.
Remove both plastic trim panels from either side of the boot section to gain access to the inner edges of the rear quaters and remove the 10mm bolts, (2 each side), that hold the bumper to the rear quater.
The bumper will now go all floppy and as you remove the outer skin, the inner Polystyrene section will fall off too.
That's it! - Took me about an hour to figure out where all the damn clips and bolts were! - All for the sake of a reverse sensor