2.7 s type brakes not working as they should they are ok when you start breaking but when you are down to about 10mph the pedal becomes very hard to push and the car trys to roll on ?

It is possible the problem is ABS related but could equally be a problem with the vacuum servo or brake booster or the "supply" of vacuum.

Certainly best practice would be to begin by ensuring the brakes at each wheel are in good order.

Test the brake servo by pressing the brake pedal vigorously several times while stationary with the engine off. The pedal should then feel higher than usual and rock-hard.
Apply the footbrake with a moderate force and start the engine without using the accelerator pedal, if possible. The brake pedal should be felt to pull itself down under your foot immediately the engine starts and stop pulling down in just two or three seconds, maybe just a second or two more if it is a diesel model.

Release the brake, allow the engine to idle for a few seconds longer and switch off. Listen carefully in the resulting silence for the sound of air leaking. This might have to be repeated several times in order to listen under the dash and in the engine compartment around the brake booster and vacuum lines. A short piece of garden hose used as a listening tube can be useful.

Once a servo has been charged with vacuum, in the absence of leaks, it should remain charged for a long time if the brake is not used - certainly hours but often months or even years is not unusual. Aplly a moderate pressure to the brake pedal and a shhhhh... sound should be heard that lasts about a second and then stops. Increase the pedal pressure and another shhhh sound and stop.

If all tests ok you can be reasonably confident the brake booster and vacuum lines are in order though it is still possible the vacuum supply is insufficient for sustained braking. A road test on a clear and safe downhill route will determine if this is so. Make a rapid series of brief brake applications at a constant speed of around 30mph and the braking effort and the feel of the pedal should remain consistent and if it does not it indicates restricted supply pipes or hoses, poor engine tune, incorrect idle speed (petrol models) or a worn or inefficient vacuum pump if it is a diesel.