Have you owned the car from new?
If not, do you know the complete history of the car?
If not you may be on a loser.
I had a small rust problem with my prior Lag 1 Hardly noticeable really, but within 5 minutes of taking the car back to Renault they categorically stated that the small rust affected area had been involved in some impact damage and also resprayed, this alleged damage hadn't occurred during the time I owned the car, therefore if it did happen it must have happened before the car was 10 months old.
I was asked to identify the garage where the repair work had been carried out, and also prove they had carried out the work to Renaults own specific procedure's
Needlessly to say I found it less difficult to carry out the repair work myself.
BTW I think the anti perforation warranty is good for 7 years. But I would guess this is only valid if the car has always been serviced by Renault thus giving them the chance to notify you of problems.
In conclusion I don't think the anti peroration warranty is worth very much really.