Cheers Ski, I have just found a really good step by step method using a dremel and some wedges, it seems to be simple in theory although I had to reread it a few times to completely get it. It takes you through cutting the skeleton making a V groove then opening part of that out with a balled drill bit and inserting a wedge to snap the rest of the skeleton. It then says to put the bubble back in the tank wedged apart with one side raised higher than the other so that it is offset. It then says the the polyps will stretch as you gradually ease it apart and eventually they will seperate on their own.
This seems quite a good way of avoiding bursting any of the vesicles and leaving the two halves susceptible to brown jelly infection.