The long term plan for the london TMA is to move the stacks further away from the airports.
The outbounds will get an unrestricted climb to at least 10,000ft. Having a TA of 18,000ft means there are more levels available for departures, especially at airports that are close together. Thus crossing tracks will be at 7/8/9 thousand feet instead of 3/4 and it should mean all airports will have freeflow on deaprtures as more levels can be issued on SIDS.
All european countries are keen on the change except the FRENCH, and it was origionally their idea!!!!
I am sure Area controllers are intelligent and sharp enough to work in altitudes aswell as FL, after all the TMA have been doing it for years!!!!