Hi not sure if you sorted out the problem but it sounds exactly the same as the one i had on an s reg of the same vehicle this year, car stopped for no apparent reason randomly over a number of months until it finally gave up in september, a nice AA man who towed me home said it sounded like a fuel pump problem, and once home proved this to be the case by removing the rear right passanger seat to access the pump where by he tapped the cover with a hammer then started the car without any problem, i noted that you could actually hear the pump running and that whilst the car was ticking over if you tapped the lid you could stop and start the pump, the AA man recomended a new pump be fitted but owing to the cost i could not afford to have a garage do the work, but purchased a second hand one and decided to fit myself since i had a haines manual which details this operation quite well, this has been done and the car now runs perfectly, however i am currently in the process of sending photos of the faulty pump back to renault and asking if they should not be recalling vehicles with this pump, you see the reason it was working intermittantly was that one of the terminals had corroded away and was brushing against the remainder of the pump terminal, i showed my dad and we both believe that it was only good fortune that stopped the terminal arcing and igniting a tank full of fuel under me and my family, if you still have the problem or have sold the car on please get it checked out or notify the new owner.
Gary
December 2008