Madhatte

Don't forget the possibility of the switch in the master cylinder--it's there to protect the proportioning between front and rear brakes--if it detects the proportioning is wrong it will light the light on the dash. It's very useful as a heads-up on brake line problems and will tell you if you need a bleed too. Since your light is intermittent and your pedal feels weird when the car is cold this is the first place I would look.