When the engine management light came on my Honda Jazz (2001 model) the car started to cut out my local garage could not diagnose the problem, but gave me the details of the fault code and recommended I take it to a nearby Honda dealer. I gave the full details of this diagnosis to Honda and the technician said that I needed to replace the coils and spark plugs at the cost of £610. Due to the age of the car I took the car away and got my local garage to do the advised work for £400. However, this did not resolve the problem and I returned the car to the dealership £400 out of pocket. I was originally advised by Honda that this was a common problem and this work would "definitely" resolve the issue - this obviously wasn't the case. On second look at the car, the dealer decided that the sensor relating to the fault code should be replaced, which seems to have resolved the problem. My question is, do I have any rights to compensation or negotiating some good will with regards to the cost of replacing the sensor, bearing in mind that I spent £400 on work that was unnecessary due to their incorrect diagnosis?