braking question 21Turbo

Got the 21 turbo back on the road after 6 months of sitting off the road due to a leaky rear caliper.I bolted on a good second hand caliper and bled the system using a one person pressure bleed kit, and then lowered the fluid level back down to the Max mark.There is still problem,which is when you push the brake pedal down it travels to a point where it feels like the pedal hits a concrete wall, and there is an audible "clunck". You can't push beyond this and when the servo's not in action the "concrete wall" feeling is right at the top of the pedal travel. Any advice would be great!!
Jack.