I have a 407 SW on a 54 plate, the steering has recently started to get stiff at times, assume the power steering isn't working properly. Somtimes feels it is pulling right other times left, then it will OK, had a look at the fluid level & its just at the bottom of the white plastic insert in the reservoir. Read somewhere about filling 25mm above Max but can't find any indication of Max. Where is the best place to get fluid to top up, from what I read up to now it seems I have to buy from Peugeot dealer but only need a small amount to top up. Hoping it is this if not what can I do to check what the problem is.