You can buy a new box for under £400 from Renaultspares in Altringham with 12 months warranty, then you just need it fitted, local garage should do it with a new clutch for less than £600, and it will be fixed in a week. By the time Renault respond and probably will not offer much in the way of goodwill, you will be so sick of the car that you will of sold it..... Unless you have a very good dealer, support on this we'll known issue is very hard work. If you don't have a full Renault service history forget it.