The exhaust fitment ended up much more straightforward than I thought it would. I have been eying up those rusty cylinder head nuts for a while now. Every-time I have done something on the bike I have sprayed them with WD40 and anything else that I thought might help with de-rusting them. Finally the day came and I grasped the spanner with trepidation but they just came undone. The old exhaust had very rusty front pipes and they almost fell off.
I removed the rusty front pipes from the silencer and kept the latter as it was in reasonable condition. The front pipes I just scrapped. They were full of holes.
The new exhaust was an identical Motad unit but with stainless steel front pipes this time. I attached at the cylinder head first and and lightly did the nuts up. I popped a bit of high temperature grease on the ends of the front pipes before stuffing them in the silencer to help them slide into place. I lifted the pipe up and inserted the rear support bolt. I gave it a few taps here and there with a hide mallet to make sure everything was seated correctly and nothing straining and then tightened everything up.
All seems to work a treat. Fired the bike up and it burbled along nicely.
Next job chain.