Babotika
From a working ATCO point of view, you are correct.
From an office/empire building/emperor's new clothes/regulator's point of view, you are wrong
10.000' is a reasonable compromise. It works with cockpit procedures and most of European ATC. If it doesn't work with future UK plans, then UK plans need to change. Having up to 40 different QNH settings in the UK, each requiring an RT transmission, and read back, is absolutely stupid and will cut capacity significantly because of RT workload. But hey ho, apparently it makes all conflicting traffic disappear and allow SIDs to go straight to 18,000'. AYE .. RIGHT.
Lunatics in charge again.