The large umbrella is good no matter what climate you are in, it fits down the side of the passenger footwell. I cannot think of anything that is 12mm spanner size on the M3W. Take an adjustable spanner rather than all the sizes. As others have mentioned, the engine is American so A/F size Allen keys but Loctite everything and it shouldn't shake loose. If you have a Leatherman or similar, the different pliers and screwdrivers can be left out.
Chances are that what ever you have tools for will not be the problem. Preventative maintenance and checks maybe aren't fashionable but they do work, better to check and fix things in the comfort of your garage than at the side of the road.
.
