<<These people work in very complex airspace, (check the Eurocontrol tables),
AND, have to cope with extremely difficult terrain clearance issues. We're talking MOUNTAINS here.
Am I not correct that the highest Air Navigation Obstruction under LTMA airspace is the Stokenchurch relay station? >>
With great respect to my friends in Manchester (where I was born about 200 years ago) this is irrelevant. Air Traffic Controllers are well familiar with their local geography and local instructions will detail the altitudes to which aircraft can be descended in safety. I dare say some of the controllers in parts of Scotland have mountains under their airspace too. Controllers know what they can and cannot do.