Hi Simon Did you ever get you frozen pipe problem solved. I have a ski chalet in Camurac (Pyrennes) and every year whilst i am away i get burst pipes even when i drain the system down there seems enough lying in the pipes to freeze. I also think my pipes have been soldered and not brazed as they do in France. I think the solder is braking down with the cold temperatures.Does'nt help that the pipes are 10mm and not 15mm which we use in the UK. My mains comes in in large black plastic pipe but i have a stop .... under ground in a hole in the garage. I have seen many french houses where the mains tap is under ground. I have never had a problem with the mains black pipes just all the copper in the garage ceiling. Hope this helps but if you have cured your problem please let me know how?? Regards Len