OK- so I've heard people say 'you don't need to buy a bottle 1st time' - you just get hold of an empty one from somewhere and get it re-filled. But where can you? I've tried the local tip and they only have 13kg - likewise the building contractor I work for. So where can I get hold of an empty 6kg/7kg propane/butane bottle for nowt ???? (Wirral area)