A special case is not paying the income tax that the company is supposed to be paying on behalf of its employees. If an employee makes £4,000 a month, and the employer is supposed to pay £1,000 tax and doesn't, that's not the employer's money, that's the employee's money. Not paying the employee's money is a much more serious matter than not paying your own taxes.
A google search found this article http://www.gaebler.com/Not-Paying-Payroll-Taxes.htm which says that a person not paying taxes for employees is personally liable, that this liability does not go away with bankruptcy, and that jail is possible.
So their advice is: Whatever other debt you have, paying taxes for your employees' payroll is the absolutely highest priority (higher priority than paying wages, paying the rent, paying company taxes and so on).