Yes, I really recommend Bimmershop! It's been recommended to me by a fellow Canadian Cooper S driver and I am planning to have my Cooper serviced by them after the warranty ends in 2007.
If you want to wait while Sebastien does the job, you can sit in a couch in his shop and watch him work on your car.
Of course it's a small shop operated by two or three people, but Sebastien is a skilled mechanic with loads of racetrack/performance experience.
The only downside is that they are far from Montreal
By the way, aren't you worried of damaging your wheels during the winter ?
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paco