Thanks Invictus, I got that now. I would imagine that all around the world the concept is the same ie. The transition altitude is constant, and as the QNH drops the transition level goes up, to in effect maintain a minimum 1,000 ft separation between the transition altitude and level.ie. The transition layer will always remain a minimum 1,000 ft.
My problem is where, one FIR has a transition level of FL100 and abutting that is an FIR with a transition level of FL140, and the problem of aircraft switching from one to another at varying points along their route, and the very real possibility of nose to nose aircraft operating in the same area but on different QNH settings, as it is now, 19 hectopascals different. For example, one aircraft operating at 11,000 ft on 994 hpa and opposite direction traffic at FL100 on 1013 hpa. I think I have that the right way around. I think you understand my concern. My question again is, why isn't it a safety driven priority, to get all FIR's the world over working with the same transition level?