Hand Brake Problems

My Peugeot 306 (1998cc Cabriolet) -V Plate - just failed its MOT due to Handbrake problems. Apparently the friction was 12% and needs to be 16%. (I have removed the centre consol, replaced the brake cables, replaced the pads, and bleed the system) but the problem is still there. I have noticed that one side is perfect (really strong) but the other side has a tendancy to have uneven brake pad wear, i.e. on the rear right , outer pad is thinner at top, and inner pad is thinner at bottom. When I remove that pads I have noticed that the brake pad housing goes flush with the disk at the top, and there is a gap at the bottom. i.e the (Bosch) brake system doesn't seem to run parallel with the Disc. Wot do I need to Replace/ fix to sort ut this problem.....many thanks!!