Your narrative admits that you parked in the disabled bay without a BB and chanced your arm, hoping a CEO did not turn up, so it's quite difficult to think of any really solid appeal argument. Sorry if this isn't what you wanted to hear.
You drove off before the CEO could have served a PCN, so he correctly put you down as a "driveaway". Under the Traffic Management Act 2004, a new process was introduced to deal with 'driveaways, which previously could not be served a PCN. Under the new process, the council can serve a postal PCN because the CEO was in the process of preparing a PCN to serve, which is why you got it in the post, not on your car.
However, your narrative also suggests a reasonable appeal argument, namely that your husband or yourself are waiting for a new BB, (is this a renwal, or a totally new one ?). You would need to provide some collateral to support your BB appeal, so include copies of your BB application.
