That was one of the reasons I wanted renault to do it, if they fit new parts without diagnosing the problem i will just take it back when it fails again!
I wouldn't count on that system working mate, dealers are very well rehearsed with cop out clauses.
If they did fail again they could for example blame the calipers, then they could agree to replace the discs & pads but only if the calipers were also replaced which would cost you a packet.
The calipers not sliding freely on their mounts is a common problem, the weather gets in between the rubber sleeves and the caliper, this causes the Aluminum of the caliper to oxidise, this oxidisation slowly builds up, as it does it squeezes rubber sleeve which then gets tighter onto the glide pins that the calipers slide on causing the caliper not to slide freely.
To cure this the rubber sleeves needs to be removed from the caliper and the bores that they sit in cleaned until they are nice and clean, reassemble with a good smear of silicone grease into the bore and on the part of the rubber sleeve that sits in the bore.
You can see how the rubber sleeves pass through the caliper in the picture below.