Philmco

I will be moving to Aude probably by early July. I would like to buy a new car (Renault or Peugeot) before driving down. I thought that I may be able to cross the channel and buy something and bring it back to England for a few weeks, before loading it up and setting off. Does anyone have any ideas about buying in Calais/Boulogne etc etc. I have a French bank account. I have heard that they will register the car in Aude for me?