Now all that is over... I can disclose:
I used multiple cloud layers, all restricted, using larger diameter for each progressively higher layer, the core of the geyser is a modded version of Ulco's volcanic plume/ cloud column... Though barely visible, so you could do without it.
)
My hdd is playing up big time, which is not good, but if possible I will experiment more and post a clip....
Cheers folks,
Away for a beer
J