Gavin traded mine in at my service in September at Discover leisure, cost me a couple of quid extra plus a new conection, l think it was new regulator at about
Traded my empty Calor in for hte new lightweight when it was empty, couple of pounds extra but it is worht it for the weight and also you get a gauge indicating how much gas you have left.
Infact i have just put the steam on in the van for a few hours to burn all the dust & cobwebs off the burner in the fire also cracked up the fridge, i have now got a indication as to how much gas is left in the bottle its indicating about 2/3 empty by the frost on the outside of the bottle.