Re: Final paragraph.
The 'bad faith' part of the Ackroyd case was that she and the BBC were claiming she was two different things*, and each claimed the other needed to pay taxes but neither paid. It was reasonably presumed to be obvious to her, or her advisers, that this could not be legal.
*The BBC characterised it as a PSC, which employed her and had to pay employer's taxes, NI, etc, while Ackroyd claimed to be working for the PSC as a self employed contractor. Frankly, it's astonishing she was advised to fight it, because this one's an open and shut case. The PSC was fine, but she was obviously employed by it - that's the meaning of personal services.
Tbqh, Ackroyd and her accountants were lucky to escape criminal prosecution, because this isn't a loophole, or a grey area, or pushing the line, it's plain, straightforward tax evasion.