2002 Jaguar XJ8 Intermittent Braking problem

Hi, lovely car, am now having an intermittent braking problem, at different times (wet, dry, fast, slow) I press the brake pedal and it feels like the pedal goes hard and the ABS is kicking in, the car then pulls to the left, I lift off and press again and brakes perfectly fine. No ABS light shows, I have had it checked by 2 garages, neither could find the fault, they checked the ABS seals, Calipers, pads, discs etc. Last garage says they think it may be an electrical problem? Sometimes it feels like the car will not stop and I have to pump the pedal several times.