Future-proofed! You haven't adjusted your hand brake properly. Wind the centre console screw OUT fully, so that the hand brake doesn't work at all (releasing the tension built up on the springs on the rear calipers - the cables should be slack at the caliper ends, and the spring mechanisms should have returned all the way to their end stops). Then turn ON the engine to start the power assisted braking. Then pump the foot brake about 20 times to push out the caliper pistons on to the discs fully (this winds them out to their maximum possible extent with the pads you have in there). Then, stop your engine again, and pull the hand brake up ONE click, and ONE click ONLY. THEN wind the centre console screw IN, until both rear discs only just start dragging on the brake pads a bit, but consistently. Then that's it. If your calipers are working fine, and the auto-tensioner spring mechanisms are not corroded or jammed (make sure the springs on the rear calipers are nicely lubed up and free moving), then you should be able to pull up on your hand brake and be fully locked on a hill at somewhere between 6 and 10 clicks (to pass an MOT). Obviously, to do all this readjustment, you should have the back of the car up off the ground on axle stands. Good luck.