No oil pressure - any ideas? - *UPDATE*

[nOO7]

Hi all,

Got the dreaded STOP low oil pressure warning the other evening in my '57 plate 2.0 4Motion Sport Estate(BKP), so being aware of the Passat's potential problems I immediately turned the ignition off (within 5 secs of the warning appearing) and towed it home. Must be the hex drive/balance shaft issue I thought, however on dropping the sump this afternoon that doesn't seem to be the case. There is a small amount of play in the balance shaft bore but the hex drive certainly won't rotate in the bore. Even a worn hex shaft that I removed a year ago doesn't slip at all though there is definitely play there.

So, any ideas on what the problem could be?
I though perhaps the oil pump itself - does anyone know if there's any way to test it off the car? Or any indications that it may have failed? The pump rotates smoothly and freely and I can see the rotor turning through the inlet port.

The engine seemed to be running fine before the problem occurred.

Any pointers/thoughts much appreciated.