Renault dont supply fixing kits unfortunately.
The easiest fix is to replace the whole regulator assembly. You can get them off
for about £60 more or less. There are instructions on how to do it on this forum. Any other garage can fit a regulator for you at a fraction of the cost that Renault would charge you.
You can also buy repair kits off
which are basically replacement thin metal wires like what has snapped on yours. You could probably do this, but it looks a right mare to do as it needs to be tensioned correctly etc etc !
If you do go down the route of changing the whole regulator, then you can swap your motor over
(assuming your motor isnt broke too). I think for the motor and the regulator combined your looking at £100, just for the parts.
Make sure you get the correct model, there is a 2 pin and a 6 pin regulator IIRC (maybe its the motor that is 2 or 6 pin
). Which one you have depends on whether or not your car has antipinch windows.