Visually, I would assert that 16-inch wheels would be compatible with a 320 model, whereas RealOEM indicates that the 325 rotors measure 311mm in the front and 300mm in the rear. I remember that the 4-cylinder diesel engines were identical to the 6-cylinder petrol engines (specifically, my 325 donor brakes). There is a sufficient inch of clearance between the callipers and my 17-inch rims, allowing ample space for a 16-inch rim.
The 330d M-Sport rotors measure 330mm and 336mm, compatible with a 17-inch rim, but not with a 16-inch rim.