WORST SERVICE EVER EXPERIENCED

My car has been at Peugeot Hatfieild for repairs for more than 3 weeks from the 18th March 2015 for a mechanical breakdown problem, it is still under warranty and i am not even contacted for progress nor offered a courtesy car instead i am the one phoning daily. I have tweeted my complain, phoned head office but up to this date there is no positive response. I made the last call today the 08th April 2015 at 15:00 and was told that they are unable to figure out what could be the problem. How on earth does it happend that a dealership dont know how to resolve a mechanical problem in a car it manufactured? In the mean time i am not even given a courtesy car nor being informed as to when the car will be fully repaired. My customer rights are being taken for granted here.