Heated Seat Problem
I'm have a heated seat On my '03 RS. It's my third one! Each one has failed after running for a long time on the high setting. So, with the latest one, I've ben very careful not to use the high setting any longer than it takes to feel the heat, then moving the switch to low.
BMW does say something to the effect that the high setting is for brief periods, but doesn't say how long that might be. If yours got hot with the "very hot" with the switch in the low or off position, I'd have to suspect the switch.
Incidentally, there are two heating elements, sharing a common ground. They are powered directly from the switch (via a fuse).