All very well having a cambelt done on the cheap or by a mate who knows what they are doing, but when, (NOT IF), it goes wrong, who you gonna call?
Renault dealers may be a lot more expensive but you will have the (genuine)belt replaced by a factory trained technician, using the correct method and special tools and have a gaurantee as well, plus a stamp in your service book.
Just for info, the tool dealers use to correctly tension the belt costs £400! Has you local garage or your mate got this tool?
Up to you. caveat emptor.
Bob