The 404 part number has both the front and the rear lights and they are used in Europe for all the M3's and it is the same part. I compared it with the switch I took out of my 2009 M3 car and looks identical, except that 404 switch has the front fog light switch which I am aware of is not used in the M3's because they don't have fog lights. So, yes the front fog light is INOP but it looks great, it is the same switch that I took out of my M3 and even BMW Europe confirmed that the European M3 switch with the chrome trim is being used in all their 3 series including M3's. I was in Germany and I went with the BMW dealer through the parts list. So, just FYI. You will be fine with the 404 part number. However, if you want to go just with the rear fog light swith than you should go with the 400 number. I am thinking about reconfiguring the front fog switch so I can use it for my front PDC system that I am currently working on. That's why i bought the 404 switch.
I am more than happy to supply pictures and you guys can see how identical it is to generic US M3 switch. Also, it looks great at night; the whole light switch panel is illuminated including the front and rear fog light switch. I cannot be happier with my choice and decision and two switches for the same price as for the the rear fog switch only - not bad.
Good luck with your research. I hope it helps.
P.S By the way, all the european parts that end with the 400 numbers on the swith do come with the chrome trim that the M3 has. Believe it or not the European switch has the crome trim regardless of the model. I don't know why the US has crome/ no crome option.