Can you still buy those reset tools of ebay ?
Sounds like a money making scam from bmw to me.
Light comes on / car runs like shite / reset service indicator and car runs well again 
Not that any reputible manufacturer would ever write anything into its software like this

That's interesting, as the service light is on, because they have it serviced by an independent, and won't pay BMW £25 every year to reset it. Does that actually happen?

As we all know, there are some things that "we know" and there are things that we know and can prove

All I can say is a mate had a old 325 years ago with the service lights on.
Started off green and worked its way down to iirc amber then red.
When it was green, the car went great.
As the amber light came on, the car would start to use more fuel and not run aswell.
He bought the reset tool (looked like a fag lighter) and pluged it in.
All the green lights came on and hey presto the car was back to normal

I don't know if its the same nowdays but I wouldn't be supprised
As mark says, it would be handy if we could read the codes