But be careful all those who sit in the 'give me ICAO FIS' camp, because not one country in Europe does FIS the same way!
True, but none in the same, quite unique, manner as the UK.
Regarding pilots barely having a grasp of the UK FIS, has anyone ever considered that that might have more to do with the underlying training and examination system than the complexity of the FIS themselves?
I do not work ATSOCAS so this is merely my take on it; but is it not simply too many variables and unknowns within uncontrolled airspace that creates the problems when controlling within it?