I have been trying this since I read Leerroy's post a few weeks ago, and the HVAC system has been working reliably, ie without the rear furnace, so there maybe something to it!
In addition, other systems, like the start/stop, have also been much more consistent with what I would expect, and I haven't had the cooling fans screaming at full speed either.
There was once when I didn't follow 'Leerroy's start-up procedure' (yes, that's its name), and the rear vents started blowing hot, but after pulling over and starting up with the procedure, all vents were blowing cold again.
It would be great if others who are having the rear furnace problem give this a go to see how consistent it is and let us know on the forum here.
With more feedback and data, Ineos may actually be able to work out what is happening and eventually develop a fix.
