I thought you might like to know that my Mini has this exact same problem, and also has Metro Turbo brakes just like yours. I understand that the wheel does sit further out than it would with standard brakes, hence the rubbing. Currently i am just living with it, but i may go ahead and cut some of the arch away.
I found out that the Metro Setup sits it out 1/4" further. None the less, I could not drive it "as is" cause it would most likely either rip the arch off, or wear a nice hole in it. I will see if I can find the time to mess with it a little bit this weekend. So many variables per mini, it's like each one is a different person, and I may have gotten a semi-retarded one. Just got to get the meds right.