I've had the same sort of problem before and phoned I the Trading Standards Office straight away, they will tell you exactly the path you need to follow AND they should give you the exact wording of any letters you need to write. In my experience the warranty company and the dealership are far more likely to react in the correct way if you word your letter exactly as they suggest, obviously including chapter and verse from you, it's a good idea not to ramble but to create a list of short sharp and ACCURATE bullet points that you require resolving. Try to get a Trading Standards Reference No. for your case too. You might feel like you're up sh1t creek without a paddle at the moment but it is surprising how suppliers react when they realise they are dealing with someone who knows their rights, writes a factual letter which is to the point without being rude and is supported by the TSO.
I hope this helps, it did for me, don't lest the b*****s grind you down and most of all don't give up So many of these companies expect you to go away, if they know they've got a fight on their hands it's in their interest to settle promptly specially if they are in the wrong. Good Luck