Carl.

I can't answer your question, but I do suggest you flush the coolant galleries and radiator with a fair bit of pressure. Mains water pressure if that is high would be a good way. To have casting sand still in the block eleven years after manufacture is extraordinary so you need to be absolutely certain it is all removed before fitting another new pump.

I thought I'd give an update....

I've had the coolant system to pieces and flushed more sand out. Also had the pump off and checked that out. The actuator moved when powered (Pins 4 & 5 on the connector are the direct motor connections) so i left it with the valves open to the radiator and re-fitted it and then left the connector unplugged. The engine is definitely pushing coolant through the radiator and eventually got to arounf 60C (It's cold at present so probably to be expected) As soon as I plugged the pump back in it was heard to move to the closed position and the coolant temp came up to 90C and stayed there. From cold it does get to 90C within about a mile so I suspect that the radiator path is now closed. Anyway we'll drive it for a while and see if the P00B700 - Engine Coolant Flow Low/Performance fault re-appears - I fully expect it to....

I'd like to know from Russell - which OEM pump manufacturer did you go for in the end? I suspect that this pump is just marginal when it comes to the thermostat temperature values which the control unit isn't happy with.

Hi - I went for an INA pump and got from Partsinmotion via eBay. 

Thanks Russell - will see how I get on over the next few weeks - really need it to be warmer to see if the radiator path opens as expected.