Let me emphasise, what follows is not aimed at Plusnet. I know nothing about them, or their disuputes with Ofcom.
But in the general case, one mischievous thought arises... When a company is deemed to need 'punishment', and there is no single executive to carry the can at a criminal level, why not spread the pain among all employees, rather than just a fine which is effectively passed onto their customers? And worse, by driving up prices to recover the fine, competitive forces allow rivals also to raise prices, so customers of other companies suffer too.
We could for example have a sanction such that Ofcom are empowered to alter the personal tax thresholds and rates of a company's wokforce, affecting all employees. Whilst still not being entirely fair on all employees, some of whom are innocent, it would be less unfair than a fine that penalises customers, all of whom are innocent.
My plan would also provide a powerful incentive in the workforce to whistleblow on bad practices, as opposed to keeping quiet in the hope that financial gains are passed on as pay rises or bonuses.