From The Observer (here):
How privatisation works
Britain used to have lots of state-owned companies that were inefficient and wasted taxpayers' money while delivering rubbish service. Now we have privatised companies that are inefficient and rip off customers, while delivering rubbish service. This is a great transformation because privatised companies are more likely to make a profit and that is a great comfort to their shareholders.
Privatised companies are still allowed to receive state subsidies as long as the money isn't used to cut prices for consumers. This way, they can be a drain on taxpayers, rip off consumers, deliver rubbish service and make a profit all at the same time. This is called a mixed economy.