as mentioned earlier Jim i don't think it wise that you use stopping distance and think time as your defence,I would stick with the fact that you made a split second decission and drove through amber as it was unsafe for other road users for you to stop abruptly.
I have been warned by policeman about going through on amber the next time i stopped, I got a serious does of foooks from the police car behind who told me i should have gone through as he had to do an emergency stop to avoid a colision.
so what we do when the lights changes to amber god knows