That's true. There is a cold air feed you can get that takes a feed from the air scoop that cools your brakes beside your fog light but it does require cutting a hole in it.

Not sure how it would work with M5. It has a dual air intake as far as I remember?

You might be able to get some simple ducting from Halfords or something and secure it somewhere near the brake intake feed.

Sorry can't remember the from bumper of the M5. I know it works in the e46 M sport bumper.