I had this happen to me as part of a string of issues with a N14 back in 2012. On mine the bore had actually gone oval and is apparently a known fault that BMW/MINI wont admit to. I spoke to a good few techs from main dealers that all said the same thing. The photo attached is the report of mine. I hope this hasn't happened to yours.
Click image for larger version. 

Name:	R55 N14 Bore Measurment Chart.jpg 
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