I spent ages trying to prove whether my electric waterpump was faulty or not, but in the end still couldn't totally prove it either way, so replaced it anyway and cured the
problem.
The pump activates when the ignition is turned on (engine doesn't even need to be started - although I believe it still runs when the engine is running too) and then it should run for a certain amount of time after the ignition has been switched off also.
The plug to feed power to the pump always seems to have a very minor voltage across it. When the pump starts and runs it's almost like a controller recognises the pump is attached and the voltage increases to 12v - BUT if the pump is faulty as mine was, the pump obviously won't start and the voltage is dropped back down to virtually nothing straight away.
I didn't want to continue running the car without it for long so just took the plunge and ordered the pump. At what it cost me, I wasn't going to risk potential turbo damage for the sake of it!
It's good to try and listen out for this noise after the engine has stopped on the LCR, but it's very easy to not notice the fact that its not working - and it won't give you any form of diagnostic fault code or warning on the dash either!