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