Sorry I haven't been about much, I have been seriously busy of late.
I did read your post, and was thinking of a reply but still dont really have an answer. I have already asked around and not heard first hand of anybody who has seen this problem... but I am one of the 'experts' on www.peachorlemon.co.uk
, and if you go there and search for "Renault" and the search through the result for the word 'paint', you will see that there are quite a few mentions of similar problems on various models.
I can only say, that Peach Or Lemon is there to express you problems with cars in public, and bad publicity for manufaturers when they desrve it can be no bad thing.. it also acts as a catalouge of sins that you can use as amunition.
You could print out the results page, highlight all mentions of poor paintwork, and then see if this will make them back down for a refund. If the dealership won't help, then try Renault themselves.
I'm afraid that I am not qualified to give legal advice in England, let alone Belgium! But I'm pretty sure you have recourse... if there are any govenmental consumer rights agencies (as there are here) then I would strongly recommend you find out what your rights are. There is nothing like walking in knowing your rights, having the evidence and shouting the odds... large companies tend to mess people around because they know that 95% of the time they will give up and go away. The other 5% often get their money back.
I know of a person here who has had a similar problems with a Volvo and they intend to fight for a full refund on their car... but as yet, nothing has happened. I'm looking for some happy endings to some of these stories.