You are all wrong Ive just found the answer so listen carefully! This fault lies at the rear of the wiper motor it involves removing the wiper motor. Carefully lever off the plastic wheel box cover clips at rear of wiper motor
and you will see three copper sprung contacts these copper strips need to bent slightly to improve their contact with the park contacts on the wheel.
Reassemble and Bobs your uncle.
L.J.B Auto's Wolverhampton, December 2008