peugeot 307 110HDI - loss of turbo with engine management on orange. - mlvc58

i have a 307 110HDI 54 plate 73,000 peugeot and the engine management light (orange) has started comin on at around 60 - 70mph and i get a loss of power, still drives but no kick behind it. The light goes off once you've turned the ignition off for 5 mins? We brought it on the 21/01/11 from a dealer and but he wants to charge us for fixing it. are we within our rights to take it further? the car is in another garage at the mo, as they are trying to suss the problem out? the have said just by running a test that its possible its the FAP thats causing other problems within that system. any help would be appreicated, like i said only had the car 3 months n a bit. grrrrrr. (this garage has also said that we shouldnt use the car while these problems are happening?)