Possible brake problem

[kevd]

Hi All. I think I may have a brake issue, that I need some advice on. The issue is; with the car stationary, and engine running if I press really hard on the brake pedal it is firm, but I can feel a definite mechanical stop that will not allow the pedal to depress any further.
Now on the road the brakes seem to work fine, however I did have to do an emergency stop when the brakes were still cold, and I could feel the mechanical stop against the pedal without being able to lock the front wheels although it felt very close to doing so. It did not feel as though I was getting full braking. When the brakes are nice and warm if I put this much pressure into the pedal I would easily be able to lock the front wheels. I am putting this down to purely the need to warm up the pads (EBC Yellow Stuff)before they work properly, but I am concerned that the mechanical stop is not allowing me to use full braking.
I have Yellow Stuff pads on all 4 corners, std rear calipers and discs, with HiSpec front calipers 283mm discs, braided hoses, I have bled the whole system numerous times including the bleed nipple on the master cylinder.
Any thoughts on this will be gladly received. Thanks

[kevd]

The fluid was replaced last year with Castrol DOT 4. Rear pads are about 40% worn. fronts only about 20% worn. all flexible hoses are within 3 years old, and are braided stainless.