In the end after much cursing from Mechanics helper (trouble and strife), i undid THE nuts, and after learning what a SCR system was i disconnected adblue tank, pulled adblue filler out the way....
Wammmm bammmm thankyou mammmm.
The old RTFM worked again.
Took most of day, but tank connected up, running and heater plumbed in.
Even though fuel gauge said 80 miles in tank, not an easy job. But next time easier.