The are some "Challenges" in the CAA doc which make interesting reading, as follows:
a. It is anticipated that there would be increases in more general workload due to a greater requirement to pass QNH values.
b. More altimeter adjustments would give the potential for more mistakes to be made by aircrews in setting the wrong pressure, although the potential error value is lower.
f. A loss of preferred cruising level for some airspace users; the proposal is to remove FL190 as a flight plannable cruising level in all pressure situations.
g. The loss of FLs, on low pressure days, is moved out of the TMA environment to the En-Route environment in the vicinity of FL190
j. There may be capacity penalties within some controlled airspace sectors.
So from the above my questions to fellow ATCOs are; Who works present UK airspace which f. / g. / j. above will affect? What do you see as the operational consequences to this change? What about present airspace with FL195 as the upper limit, what happens there?
Then there is also the below taken from the following website:
Roger-Wilco | Transition altitude
"Is there a problem with the transition altitude?
Well, perhaps you will be surprised to hear that there have been numerous loss of separation incidents, some of them quite serious, in Europe in which altimeter setting errors were found to be major contributing factors.
While the concept and use of the transition altitude may sound simple and straightforward, there are two aspects of the transition altitude as implemented in Europe that harbor the potential for mistakes.
First of all, there is no uniform transition altitude in Europe. Clearly, States with high mountains will always have a different transition altitude from those with no mountains to speak of but even these latter have not come to any kind of agreement as to where the transition altitude should be. Such disparity and eventual uncertainty in the cockpit can easily lead to errors.
Then there is the process of changing the altimeter setting itself. With a transition altitude around 5000 feet, the change has to be made during a phase of the flight that involves high workload, another factor that brings with it the potential for errors.
Taking them together, those two aspects of the altimeter setting procedures do constitute a measurable risk to safety.
What is the solution?
The answer is relatively simple: raise the transition altitude to a higher level, agreed on a European scale, with exceptions only where high terrain makes the commonly agreed level inappropriate.
However, this is easier said than done.
The matter has been on the agenda of various international organizations at least since May 2000 when the Technical Director of the UK Guild of Air Pilots and Air Navigators first raised the subject at EUROCONTROL. A subsequent survey found that there was indeed a wide variation of transition altitudes in Europe and the variations extended even to considerable differences from the applicable ICAO provisions related to the establishment of transition altitudes.
It also became apparent that the specific local interpretation of the transition altitude was used at some places, especially in the military context, as a kind of airspace organization and “default” separation tool and hence any proposal to change it was being opposed not so much on the ground of the transition altitude as such but the impact the change would have on the airspace organization built around it.
As the years dragged on it became increasingly apparent that while raising the transition altitude to around 12,000 feet might be acceptable for some States, having a region-wide practically identical transition altitude was basically out of the question.
However, the nature of the problem is such that only the combination of both raising and harmonizing the transition altitude can bring the desired safety improvement.
New impetus
In the meantime various studies had shown that any raise up to and including 10,000 feet would yield basically no improvement while going to 18,000 feet (as used in the US) would in fact be the most effective solution. This is now also supported by IFALPA as the altitude best meeting the pilots’ needs.
Of course it also became clear that if non-uniform transition altitudes differing from each other by one or two thousand feet were a problem, non-uniform transition altitudes differing from each other by more than 10,000 feet would be an even bigger problem to safety.
While there were States who would have implemented 18,000 feet without delay, they had to hold back because of neighboring States who were reluctant to accept any change.
Getting fed up with the obfuscation, the UK and Ireland, taking advantage of their somewhat “isolated” airspace, decided to unilaterally implement 18,000 feet as the transition altitude starting in 2013.
More recently even the European Commission has joined the fray stating that they considered the time politically and technically ripe for putting an end to the transition altitude saga by implementing a safe solution meeting the industry’s requirements.
The question of transition altitude is on the agenda of most FABs also tough this is a double edged weapon since transition altitude harmonized on the FAB level represents only a half solution, as mentioned earlier.
A solution in sight finally?
All studies performed over the years delivered conclusive evidence that 18,000 feet is a good choice for transition level wherever terrain allows. While the 18,000 feet transition level in the US has not been without incidents, the level of safety demonstrated over there is also convincing. One should also keep in mind that the UK and Ireland must have performed all necessary analyses of the options before coming to their decision to go for 18,000 feet. It is also clear, well, even common sense, that not harmonizing the transition level would only perpetuate a situation that has been shown to be a safety risk.
With the matter once again on the agenda of the appropriate working groups and with the EC also lending its weight to push for a solution it is not unthinkable that a safe and efficient solution will finally be agreed and the matter can be put to rest once and for all."
So I can see the high level pressure being applied to the change.....