I'm failry sure the rear calipers are not a problem. I'm not experiencing uncontrolled rear slides. When the esp light flashes on tight corners I'm not braking at the time. There are no problems braking in any direction. the locking of the rear wheels is when attempting sharp turns - regardless of braking.

I'll see to the other points you mention with regard to cleaning the sensors. Just wondering why nothing is showing up as faulty on the ecu ?