Just wanted to chime in with my experience on the Cooper S. I've been having issues with the car stalling when starting uphill from a stop. At first, I thought it was just a issue with the transmission but after researching and checking the forums, I found that it's likely due to the engine oil level being too low. Checked the manual and indeed it said to check the oil level every 1,000 miles which I hadn't been doing.
After topping off the oil, the stalling issue disappeared. Just wanted to share my experience in case anyone else is having similar issues.