Rover 420 1999 rear disc handbrake not holding help needed plz?

Hi, i have a 1999 rover 420 16v dohc saloon bubble shape,
I virtually have no handbrake holding the car arrrggh!
I have replaced the discs 6months ago, then replaced the pads 2 weeks ago, adjusted the handbrake cable at the lever in car as per haynes manual,
i have the MOT due end of this month and can't get the handbrake to hold on enough to stop it moving on a slight incline let alone pass the MOT.
what i did find when replacing the pads, was that they had worn down to the metal at the bottom of the pad and almost new on the top edge of the pad, this was both sides.
i have not checked since changing the pads 2 weeks ago,
i'm sure the cable is not stretching as it stops agains the stop on the caliper,
can anyone suggest what to do next, other than replace calipers and cable, i'm at a loss??
thanks in advance Rob