N14 Engine - where does all the oil go???

That's me had my Cooper S (07) for 6 weeks now and in that time I've gone through over 10l, yes, 10 litres of oil!!! There are no evident oil puddles under the car so I'm guessing it's going somewhere it shouldn't and then dumped out the back. I can occasionally pull off a James Bond move and leave the car behind me in a cloud of smoke but it's not as bad as it was since we ran Sea Foam through it. I had it in to JC's to get roof bars fitted and they gave the car the once over, when up on the ramps it was pretty evident there was more oil on the engine than in it but the tech couldn't specify where the oil was coming from as there was so much of it. They have recommended getting the engine stripped back and cleaned to try and source the problem. One thing I did discover at the weekend after finally checking my spark plugs is that one of them is missing a chunk so I'm assuming it has disappeared in to the dark oily depths of my engine doing god knows what damage on its travels. Anyone else had this sort of oil consumption issue or am I just lucky?? :frown: