Disco TD5 Brakes come on their own!!

Hi, can anybody help? A few eeks ago, the front brakes on the disco came on while driving up the motorway. Got a repair, new master cylinder, discs and pads and fluid.all has been well for about 2 weeks. today, the same thing has started happening. The brakes come on, pedal goes rock hard and progress is slowed. If I pull in and turn off the engine, it seems to be okay agaion for a few miles. Had it checked at the garage but the test equipment shows no faults to the braking system. Used it again, drove about 14 miles and the same thing has happened. The fault now seeems to be intermittent, going off when you stop, sometimes worsening when in traffic. Any ideas anybody? I don't want to have to replace the ABS modulator at the cost of enough limbs to stop me driving anyway! Your help would be much appreciated.

its probably faulty abs sensor or wheel brg just starting to wear abs ,tc and hd work off same sensor system can get confused and apply brakes on some venhicles

Thanks, will get it looked at.Cheers.

Update on the brake fault. Trawled loads of threads about brakes, got a bit scared thinking bout the abs regulator! Ayway, found a bloke who had similar problem on model without abs. Anyway, talked my mechanic friend into the idea of the calipers being faulty at reat (after checking temperature of the discs by hand after every journey) and found offside rear stinking hot! He's done the calipers, discs and pads and the difference is amazing! Steering and everything is better, breaks are great, acceleration is ace. Must have been a problem for some time creeping on. Still can't explain why its happened just know its fixed thank goodess!