Selective benefits
Doubtless "Big Airways" will benefit from NATS preferential treatment. Others do not. I reckon Baby/Easy burn at least a third of a ton extra on every flight from Bristol to Scotland due level capping, and Ryan/Easy/Baby must burn at least an extra half a ton from Bristol to NI capped at FL240. I suggest that two days a week the level capping should be reversed and selected London-Scotland/NI's should be capped in favour of Bristol/Cardiff deps.
So far my personal experience of "270knots" indicates that there has been no effect on reducing stack holding....but there has been an increase in R/T loading on already congested frequencies.
Additionally....for years I've used my professionalism and experience to monitor stack delays....and my colleagues and I have informed the crews in timely manner and applied speeds as required.....but only when required.