Reading between the lines, I reckon that your front discs are glazed, and this is causing the squeal. The fact that the noise stops when you brake is a sure sign. Ideally the garage should remove the disc pads, clean them, apply copaslip grease to the backs and reassemble. Hopefully they should have already done this - if they have, I reckon that the pads and discs should be renewed as a set. PS Renault will charge a fortune for this - using pattern parts is much cheaper and just as good. Example - Renault discs £130 a pair. British made pattern ones £60 pair. See what I mean?
John
January 2008