I have operated out of Uk a few years back on heavy jets into and out of all the world hubs. also operated in US and UK military controlled areas of the Middle East .Before that operated in Africa.
Now operating in Australia.
In my opinion UK and US ( military and civil) controllers are top notch.
Best London area after engine fire in flight.
Aussies pedantic but correct.
Africa, South America, Asia ......WTF (Dubai and SA excluded)