Update: I got INPA recently, and it seems the clever little ECU knew all about the water pump failure. Including what the milage was and pump current, voltage, temp, rpm etc...
But some bright spark at BMW deemed that neither water pump drawing zero current, nor running at zero rpm was worth bothering to light the MIL!!! Well done!
There was even a log of comms loss to pump when I unplugged it... Yet again no MIL!!!