How can i fix my Bosch Dishwasher Model SGS43T22GB empty/fill problem, ?

Any clever Bods out there who can help me
I have a Bosch Dishwasher Model SGS43T22GB. (the newer model was called classixx but looks exactly the same)
Over half way through its cycle before the rinse cycle starts, it gets stuck on fill empty, fill empty, fill empty and so on.
It does not completely empty when stuck, there is water still in the bottom, its as if it is just topping up the water then removing a bit.
had it apart and no blocked pipes etc
Any Ideas anyone,
Thanks