I would send it back, if your sure its too short you dont want it popping out and causing serious damage, even at full lock it could slip on the splines. I seem to remember there being 5 different driveshafts for the drivers side across the 172/182 range. I can give you the measurements for the 172mk1 shaft, but it will be pointless as that one is a lot shorter than them all.
If you dont mind a trip to nuneaton, give gordon (02476642331) at Renault SRS a call, he will sort you out.