Well guys the job is complete and the difference in the room is staggering!
The strange thing was I started this thread as my back row was impossible for me to use, the boom from behind certainly was not nice to say the least. The strange thing is after all this exercise, I now prefer the back row the best, the bass is clean, deep, fast and alive, the boom has gone!
In the end I added to the back wall four 3" wrapped fiberglass traps with 1" air gap behind. Two long 2" fibreglass panels (both sides of room) with no air gap behind as the door has to open up against the side walls. I also made a ceiling one over the projection port, 2" thick no air gap. Still don't know if technically what I did is totally correct but there were always limitations with the space I had. What I did may not be correct mathematically, but the end result in the room is great and that's what's important I suppose.
I'm very happy and I thank all those who helped me along the way, especially Ethan.