I have had the throttle jam flat out on a BA as well, was lucky I turned the car off straight away and rolled to a stop, once stopped I then heard a pop, the pedal just poped back up off the floor, I searched for the cause but never found a problem, and I have never been able to make it stick down again (while the engine not running of coarse), only incident after owning 2 BA turbos over 8 years, just a freak thing to happen I guess, and it can happen, in a panic and if it happens again to anyone here try to keep your wits and switch off the car and roll to a stop on the brakes