so its high enough to hurt, but low enough that the lowlives won't immediately go into receivership?
Nope. Buying an off the shelf company is cheap enough circa £50, and that's the marginal cost for the bottom feeders. The forces of government could follow up "wilful insolvencies" through the Insolvency Service and the courts, and bring them to book, get them struck off as directors, but its slow and ineffective.
The only real recourse is to prevent directors and shareholders hiding behind limited liability in this way. Government could have closed this loophole years ago, but they're too sluggish and idle. Limited liability is a hugely important concept, and should be protected and encouraged, but at the moment government simply let the status be abused.
Biting the hand that feeds IT
