Promises and passing the buck

I bought a Mercedes Vito in 2015 with a faulty ignition and was promised it would either be replaced or they would put me in another vehicle if the problem could not be rectified. To date I have only experienced more promises that it would be replaced and feel my issue has been neglected blatantly. Again it's been another month past and still no joy ? What next, legal action or approach our local newspaper with the hope that something will finally be done about it. ?