Megane paint blistering

I'm having on-going dialogue with Renault regarding exterior finish problems with my red 2005 Renault Megane Cabriolet. About 24 months ago, I raised a query with my dealer about blisters that were appearing on numerous panels, the Service Manager took pictures and forwarded the details to Renault. No one got back to me directly, but the comment was made that it was out of warranty. The exterior finish quickly advanced from small pimples to massive blisters. A panel shop I took it to say the entire car needed to be repainted and I was quoted $7600 for the job. The opinion from the panel shop was that it was caused by poor preparation, which was backed up by two paint manufacturers when I contacted them. When the Renault dealership I had been using closed I shifted to another dealer in Brisbane. When the Service Manager checked the vehicle in, he said he'd never seen a car of this age looking so bad. He phoned Renault's warranty manager while I was with him, stating similar and felt they ought to have a look for themselves. The response was that they already knew about this vehicle and that it is out of warranty, end of story. The long and short of this is that the car is a total embarrassment to drive and should be to Renault as well. As far as I can tell this car is a lemon that has had some aspect of the manufacturing process performed incorrectly. I have not been able to find another Renault that looks at all similar in condition to mine. No one from Renault has inspected the vehicle, but they authorized and paid for DuPont to conduct a visual inspection of it. I have not been able to get any conclusive answer as to why my vehicle is so bad, but everyone who has seen it to date agrees that Renault should be showing far greater interest in it. Renault puts it down to "age and weather", to which my response is that it is "unfit for the purpose for which it is intended" and the opinions I've gained from industry professionals seem to agree. The company has offered to pay half of the cost of rectification, leaving me to pay $3800. I have told Renault that their offer is inadequate and what I seek is a car that looks the same as other cars of the same age and model, not half done or half price, only fair and reasonable I believe given the circumstance. What are your thoughts?