Chevron - agreed, but as an ATCO I tend to only read this forum. Also I would have thought that other ATCOs would like to talk about this subject.
We have a lot of USA ATCOs reading this, who can contribute from their side, where this is the norm.
I can imagine some flights/airspaces which presently cruise/use FL180 / FL190 in the UK may have issues.
Mods - please keep this open for valid ATC comment, however if common consensus is this thread is not required, then please delete it.