Finally after a couple of aborted attempts I have dismantled the IRS into its major component parts. The key lesson for me here was how hard to hit the lower suspension shaft to get it to exit the extremely tight housings. It took me a while to raise the courage to hit it very hard to get them to budge! The only other issue I encountered were the shaft nuts were eroded onto the shafts on the forward facing side and I have had to cut them off without damaging the shaft threads. I was amazed how effective the Dremel was as cutting through metal.
Next job will be to dismantle the brakes from the differential and to clean all the parts prior to sending to Gerry to be modified or away to be professionally refurbished.