my brake lights are staying on when the pedal is pressed hard. it seems that the push rod from the cylinder to the pedal is sticking slightly and not returning out far enough to cancel the brake light when you take your foot of the pedal. any ideas - faulty cylinder maybe!

Not an answer, I know, but I have been having the same problem - see here. I am in the process of putting a return spring mechanism on mine to see if that helps.