I posted a while ago about how my 320 has developed a rather bad oil leak, its a 320i and if its parked on the flat it hardly drops anything, however if i park up front end first up a slope, i.e. on my nans drive this happens

it was only parked up for about an hour...obviously my nan was pleased

so now everytime i go i have to reverse up the slope and it drops no oil....
Where the hell is it coming from? any ideas?