Wow, I'm impressed that you keep notes Mark
Is there any simple way to shield either the CAN wiring or Cruise Control unit from each other.
Not really, I don't think that it would be that easy or practical.
However having said that, I have used adhesive copper tape for RF shielding before. Maybe one of the vulnerable area's of the loom might be the first few inches of wiring exiting the chassis/engine connector, including the splices. It looks to be a bit of a birds nest and would hazard a guess that the twisting of the CAN wires is not great there. You could possibly get access to wrap the bundle in copper tape. That might help to protect from noise outside of the loom and from those near power wires, that I think you may have introduced? It's something perhaps you could try for a while and rip it off again if not needed, with no harm done.
Don't forget to ground the copper tape though!
