Starter motor mate, the buzzing is the coil failing to engage, there is only 1 thing to try prior to replacing it, engage 1st gear and push it, just enough to trun the engine over, about 1 or 2 jumps of the gear, then try restarting the car, if it starts the the coil is ok and the gearage of the starter is at fault, if it dont start its the coil, either way a new one should sort you out.
Talking from an ex DENSO employee that used to make and test the things
WS
May 2009