Yeah, I know what you mean.
I've got several oil leaks on mine but they're proving hard to trace. One in particular seem to come from between the 'big plate' on the front of the engine and the block. It runs down the side of the block under the alternator. I noticed it when I first got the van and checked the condition of the cam belt. It seems like it could be from any one of the seals that go through the front plate.
Despite all this the transit leaks less oil than any other vehicle I've owned so I'm not really that worried!
Steve