Foot Brake Problems

[mad sparky]

i am recently suffering problems with the brake pedal sinking down at least half way to the floor before the brakes actually take effect although if you pump the pedal it does harden up, i've had the master cylinder replaced and the system pressure bled, with no outstanding improvement .

I have been told that the servo appears to be working normally, but am now struggling to come up with a reason or solution to this worrying problem, has anyone suffered this problem and found the magic solution would be grateful if anyone could guide me in the right direction ?.