Yeh!!
Cracked it and now back together again. The problem was not screws through the top handle unit, this only comes off with screws from underneath. Eventually brute force allowed me to open up both sides. There was a problem however:
The three silver screws on the top of the service side that MVacs highlighted in read above hold the drum brake and if removed that unit will twist and jam. Once I had the unit apart is was reassembled with that part reattached and everything went back together quite easily.
So DO NOT remove these screws to crack the case open.
I am taking photos of reassembly and will extend this thread with a more comprehensive guide for this vac when I have a bit of time.