yeh i had same problem fitted new accumulator every thing now works finechange the acumulator (round ball thing on top of abs pump)had exactly the same problem on mine and cured it also several others on here remember to press the brake pedal 30 times i think to get rid of the pressure with ignition off some threads on here to confirm how to change though is really easy though
then you need to read the fault codes ,otherwise its a stab in the darkI just changed the accumulator : dead simple : didn't have to re-bleed. ( didn't fix my prob tho' !!