Considerable improvement by brewing at far too low a temperature and too coarse a grind. Still not a great coffee. But I have renewed enthusiasm. A more scientific process may ensue over the coming weeks.
Register interest in my findings and I will share. I feel like this is a similar situation to a question I asked someone a while ago though...
ME: Pat, my new disc brakes squeal, how does one stop disc brakes squealing?
OLI: (butting in whilst slowing down effectively in the wet on a >20 year old mountain bike) Get rim brakes.
PAT: (no reply)