What is a UCH?
This maybe bollox no guarantee you will see a result but maybe write them a letter threatening legal action and see what happens. Something like, On (date) i purchased the vehicle (reg, make) and it developed the same fault over the course of 3 years (explain how the occurence of the fault is not usual or reasonable even out of warranty and how you made attempts to bring it to their attention within the warranty period or something). s14 of the sale of goods act 1979 require you supply goods of satisfactory quality. the fact that the vehicle developed the (fault) shows that it was faulty at the time of purchase. It was there not of satisfactory quality and you are consequently in breach of contract. In the circs, i am legally entitled to financial compensation. However, while fully reserving my rights under the sale of goods act, i am prepared to give you an opportunity to repair the (fault) without any charge to me. I look forward to receiving your proposals for reparation within the next 14 days.