Very nice car. I too live in the Vancouver area and just got my 335i M Sport in EBII. Right now I am running the 19 inch with summer performance. Therefore I am not driving it much in the sub freezing temperatures we are having right now as the tires aren't optimum. I have an old car to use at present. I too have the M sport brakes which are very nice and very dusty! Next summer while I have lots of time I am going to see if I can order up a set of 400M 18 inch rims and get a set of dedicated snows put on. I am pretty sure the 400M rims will fit the M sport brakes as that is an option setup on the BMW configurator.
Your wheels look pretty darn smart as well - I could live with that as a winter setup. Dedicated winters are the way to go. All seasons are a compromise no matter what the season. I think you are much better to have dedicated winters November through March and then switch over to summers. Expensive option but for maximum motoring pleasure the best idea.