Having decided to go away over the Christmas and New year period and because of the cold I decided to change gas bottles to lightweight bottles of propane. This cost an additional £5 per bottle only to find out due to the lack of lightweight bottles in circulation when exchanging for refils could only find heavy bottles. This meant losing my new light bottles and rearranging the load for the return journey to keep the nose weight down. A real pain and costly lesson. I have since found out its possible to exchange heavy bottles for light if a supplier, say a petrol station, has some and at no additional cost when refilling, would this be wrong ??????