>>It would be most unlikely for even the most abstinate person to produce a reading of 0.00<<
I'm not exactly abstinent and that's what I've blown each time I've been tested over the past several years. I realize that alcohol testing and locked cockpit doors are novelties in the UK but we've lived with both for quite a while in the States.
All the arguments about mouthwash and ripe fruit have been tried without much success in pilot hearings in the U.S. Usually the best defense has been to hope for a paperwork irregularity like a missing signature or wrong date on a form. A couple of pilots where I work have beat the rap due to faulty technical procedures in the testing. If that doesn't work, check into rehab and demand your job back since as an alcoholic you have a disability that the employer must accomodate under the Americans with Disabilities Act.
Here's a recent example of the "hop into rehab" maneuver:
"Two America West pilots accused of being drunk when they tried to fly a jetliner have been in alcohol rehabilitation, prosecutors said. Lawyers for the pilots, Thomas Porter Cloyd and Christopher Hughes, requested a hearing to ask a judge to delay their Aug. 1 [2002] court appearance because the pilots will be in rehabilitation until Aug. 2, said Ronald Ramsingh, an assistant state prosecutor. The pilots entered the 28-day program in Arizona after they were arrested July 1 in Miami, Mr. Ramsingh said." - from the New York Times July 23, 2002