The Financial Ombudsman Service was set up by the UK government and is the official expert charged with sorting out any problems with any financial services.
If a customer and a business can not resolve a dispute themselves, the FOS would step in and provide an unbiased answer and solution to the situation at hand.
When a customer is deemed to have been unfairly treated then the FOS has the ability to bring forward legal proceedings to put things right.
In the case of Lloyds PPI, the FOS were initially charged with investigating the issues brought forward by unfairly treated and mis-sold PPI customers.
Further Reading: FOS Website.