Removing rear wheel rotors to change handbrake lining on BA XR8

It might sound like a stupid question, but I have removed the rear wheel, removed the caliper, loosened the handbrake cable right off, there is supposed to be a screw opposite the inspection/adjusting hole in the rotor that you remove and then rotor is sopposed to come off.

Problem is, it dosen't come off.

ANY HELP OR IDEA'S WOULD BE GREAT..
TA