I'm not sure what the MMC warranty period is for an M3W, but if it's 2 years hopefully the car is still covered.
Failing that as you pointed out to the dealer (hopefully backed up in print/email) that the car was dropping oil from day one - he really will have to face up to the fact then that it is a warranty claim. If he fails to react send him an email copied to the factory M3W man stating the facts and time frame.
Very shoddy advise from your dealer I'm afraid to say - perhaps he needs his hole blocking up as he clearly is leaking BS ?
Good Luck.
