Engine noise

Hi I *** you can help with this nightmare im having. I have a Ford Mondeo 2002 2. Ol Diesel which has recently had a new starter motor. When I turn the key to start the engine this makes a strange whirring sound. When I turn the key again this starts straight away. I have had the car back into the garage and had the starter motor and fly wheel checked and both are fine. They have also blown out as much clutch dust as possible in case this is having an affect but its not made any difference. Please say you have come across this before and you know what the problem can be. Thank you. Daniel.