Hi Roger
What a carry on! I think that you should push this on a bit, but taking your report at face value, I feel that Nissan need to shoulder some of this too, not just the dealer. After all they don't make the clips that have been missing for nearly half a year! Nissan GB are too quick to drop all the blame on to the the dealers top lip IMO. I would ask the the dealer AND manufacture to get together, and put you something together WHEN the full issue is rectified to your satisfaction. I would do this by letter and send the GM of the branch and the contact at Nissan GB Customer services the same letter, hold them both responsible for the issues you have had and your loyalty to the brand etc. They should present something together, I feel.
Baring in mind I have worked for other brands who frankly would have possibly replaced the whole car by now, to that value!!