Down gear and turn the motor off... simply downgearing may or may not stop the car completely. It may damage the transmission, but if you're in a situation that calls for an immediate stop, a ruined transmission is the least of your worries.

I lost my brakes in a VW in the mid 70s. I hit the back of a parked car - ours. My baby rolled from the seat to the front floor board (that was before carseats and wearing seatbelts were mandatory). I stopped, but not the way I had hoped. It WAS scary. It happened in a flash.

I'm glad you had your head about you ladyjane and am so glad you are ok. But, just think, the Lord might have put you in this situation to prepare you for something bigger, or to save you from something worse - former, you are more prepared for what to do, along with being made aware of maintaining your vehicle & latter, you are getting your brakes fixed.
Blessings....