Just an update on the smaller gas bottle idea. I cut down an empty slim Go Gas bottle and soldered the bits together and it seemed fine. However on attempting to re-fill it with lighter gas the valve popped and fell inwards. On cutting it open, I found the heat from the soldering had melted the plastic valve holder! That was unforeseen!!
Will try it again when I have another bottle but using J B Weld this time?
Steve.